Background-MRI has the potential to visualize radiofrequency ablations (RFA), which have become t... more Background-MRI has the potential to visualize radiofrequency ablations (RFA), which have become the preferred treatment strategy for many arrhythmias. However, MRI patterns after RFA have not been well investigated.
The design and application of a two-wire electrophysiology (EP) catheter that simultaneously reco... more The design and application of a two-wire electrophysiology (EP) catheter that simultaneously records the intracardiac electrogram and receives the MR signal for active catheter tracking is described. The catheter acts as a long loop receiver, allowing for visualization of the entire catheter length while simultaneously behaving as a traditional two-wire EP catheter, allowing for intracardiac electrogram recording and ablation. The application of the device is demonstrated by simultaneously tracking the catheter and recording the intracardiac electrogram in canine models using 7 and 10 frame/sec real-time imaging sequences. Using solely MR imaging, the entire catheter was visualized and guided from the jugular vein into the cardiac chambers, where the intracardiac electrogram was recorded. By combining several functions in a single, simple structure, the excellent tissue contrast and functional imaging capabilities of MR can be used to improve the efficacy of EP interventions. This catheter will facilitate MR-guided interventions and demonstrates the design of multifunctional interventional devices for use in MRI. Magn Reson Med 47: 594 -600, 2002.
International Journal of Cardiovascular Imaging, 2009
Multidetector computed tomography (MDCT) using 64 detectors is widely used for cardiac imaging in... more Multidetector computed tomography (MDCT) using 64 detectors is widely used for cardiac imaging in the clinical setting. Despite promising results, 64-slice MDCT has important limitations for cardiac applications related to detector coverage, which leads to longer scan times, image artifacts, increased radiation and the need for higher contrast doses. The advent of wide or full cardiac coverage with 256- or
Journal of the American College of Cardiology, Jan 7, 2004
The goal of this study was to determine the magnitude and mechanisms of hemodynamic improvement o... more The goal of this study was to determine the magnitude and mechanisms of hemodynamic improvement of an automated, load-distributing band device (AutoPulse, Revivant Corp., Sunnyvale, California) compared with conventional cardiopulmonary resuscitation (C-CPR). Improved blood flow during cardiopulmonary resuscitation (CPR) enhances survival from cardiac arrest. AutoPulse CPR (A-CPR) and C-CPR were performed on 30 pigs (16 +/- 4 kg) 1 min after induction of ventricular fibrillation. Aortic and right atrial pressures were measured with micromanometers. Regional flows were measured with microspheres; A-CPR and C-CPR were performed with 20% anterior-posterior chest compression, with (n = 10) and without (n = 10) epinephrine. A pressure transducer was advanced down the airways during chest compressions (n = 10), and magnetic resonance imaging (MRI) was performed. AutoPulse CPR improved coronary perfusion pressure (CPP) (aortic - right atrial pressure) without epinephrine (A-CPR 21 +/- 8 mm...
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2015
Impaired catecholamine handling in the viable infarct border zone may play an important role in v... more Impaired catecholamine handling in the viable infarct border zone may play an important role in ventricular remodeling and lethal arrhythmia. We sought to get further biologic insights into cardiac sympathetic neuronal pathology after myocardial infarction, using multiple tomographic imaging techniques. In a porcine model of myocardial infarction (n = 13), PET and MR imaging were performed after 4-6 wk and integrated with electrophysiologic testing and postmortem histology. PET with the physiologic neurotransmitter (11)C-epinephrine, which is sensitive to metabolic degradation unless it is stored and protected in neuronal vesicles, identified a defect exceeding the perfusion defect (defined by (13)N-ammonia; defect size in all animals, 42 ± 12 vs. 35% ± 12% of left ventricle, P < 0.001). In a subgroup of 7 animals, defect of the metabolically resistant catecholamine (11)C-hydroxyephedrine was smaller than epinephrine (41 ± 8 vs. 47% ± 6% of left ventricle, P = 0.004), whereas def...
We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial per... more We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial permeability transition (MPT), was present in a translational swine model of heart failure with preserved ejection fraction (HFpEF). Cyclophilin D is a key component of the MPT pore, therefore, the purpose of this study was to test the efficacy of a novel cyclosporine (CsA) dosing scheme as a therapeutic alternative for HFpEF. Computed tomography (CT), two-dimensional speckle tracking two-dimensional speckle tracking (2DST), and invasive hemodynamics were used to evaluate cardiac function. CT imaging showed 14 weeks of CsA treatment caused eccentric myocardial remodeling (contrasting concentric remodeling in untreated HF animals) and elevated systemic pressures. 2DST detected left ventricular (LV) mechanics associated with systolic and diastolic dysfunction prior to the onset of significantly increased LV end diastolic pressure including: (1) decreased systolic apical rotation rate, longitudinal displacement, and longitudinal/radial/circumferential strain; (2) decreased early diastolic untwisting and longitudinal strain rate; and (3) increased late diastolic radial/circumferential mitral strain rate. LV mechanics associated with systolic and diastolic impairment was enhanced to a greater extent than seen in untreated HF animals following CsA treatment. In conclusion, CsA treatment accelerated the development of heart failure, including dilatory LV remodeling and impaired systolic and diastolic mechanics. Although our findings do not support CsA as a viable therapy for HFpEF, 2DST was effective in differentiating between progressive gradations of developing HF and detecting diastolic impairment prior to the development of overt diastolic dysfunction.
Journal of Interventional Cardiac Electrophysiology, 2004
Introduction: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly b... more Introduction: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly being selected based on anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures, we evaluated whether stereotactic catheter guidance might facilitate anatomical catheter navigation and RFA to the great vessels, the fossa ovalis and the left atrium (LA).
Heart rhythm : the official journal of the Heart Rhythm Society, 2014
Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ... more Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ventricular (LV) decompensation suffer from nearly 50% early mortality. Whether cardiac resynchronization therapy (CRT) improves hemodynamic status in this condition is unknown. We tested CRT in this setting by using a canine model of delayed lateral wall (LW) activation combined with 2 hours of coronary artery occlusion-reperfusion. This study aimed to evaluate the acute hemodynamic effects of CRT during and immediately after MI. Adult dogs (n = 8) underwent open-chest 2-hour mid-left anterior descending artery occlusion followed by 1-hour reperfusion. Four pacing modes were compared: right atrial pacing, pseudo-left bundle block (right ventricular pacing), and CRT with the LV lead positioned at either the LW (LW-CRT) or the peri-infarct zone (peri-infarct zone-CRT). Continuous LV pressure-volume data, regional segment length, and proximal left anterior descending flow rates were record...
Heart failure constitutes a major health problem in USA and Europe. Angiotensin converting enzyme... more Heart failure constitutes a major health problem in USA and Europe. Angiotensin converting enzyme inhibitors and _ blockers were shown to reduce morbidity and mortality in patients with CHF. Yet, their effectiveness is limited. A significant number of patients with heart failure manifest myocardial conduction abnormalities. Conduction abnormalities, especially in the form of left bundle branch block (LBBB) may be
Background-Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 m... more Background-Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 major factors: (1) low defibrillation success rates and (2) persistent post-countershock myocardial dysfunction. Biphasic (BP) waveforms may prove capable of favorably modifying these limitations. However, they have not been rigorously tested against monophasic (MP) waveforms in clinical models of external defibrillation, particularly where rescue from prolonged VF is the general rule. Methods and Results-We randomized 26 dogs to external countershocks with either MP or BP waveforms.
Background—QRS duration is commonly used to select heart failure patients for cardiac resynchroni... more Background—QRS duration is commonly used to select heart failure patients for cardiac resynchronization therapy (CRT). However, not all patients respond to CRT, and recent data suggest that direct assessments of mechanical dyssynchrony may better predict chronic response. Echo-Doppler methods are being used increasingly, but these principally rely on longitudinal motion (ll). It is unknown whether this analysis yields qualitative and/or
Journal of Nuclear Cardiology - J NUCLEAR CARDIOLOGY, 2010
Cardiovascular computed tomography (CT) is one of the most impressive advances in the non-invasiv... more Cardiovascular computed tomography (CT) is one of the most impressive advances in the non-invasive diagnosis of cardiovascular disease in the last decade. Going beyond coronary calcium scoring, cardiovascular CT is capable of identifying calcified and non-calcified plaque, percent stenosis, cardiac structure and morphology, and left ventricular systolic function. The abilities to detect subclinical and obstructive atherosclerosis and exclude disease with high diagnostic certainty are its greatest attributes. Single-center and multi-center studies in various cohorts have established that CT coronary angiography (CTA) is an accurate non-invasive test for determining percent stenosis which can be performed with low radiation dose. 1-7 However, it is important to point out that coronary CTA is an anatomical test that does not provide important physiological data. In fact, the value of CTA for predicting the presence of myocardial ischemia is limited. 8-10 While coronary CTA has an excellent negative predictive value, it is more limited in determining the significance of stenoses in patients with disease. Thus, caution needs to be exercised when adopting cardiac CT clinically. The importance of coronary physiology for diagnosis, prognosis, and guidance of therapies must not be ignored.
Background—MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as... more Background—MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MRI. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. Our aim was to determine whether these modern systems can be used in an MR environment. Methods and Results—We tested in vitro and in vivo lead heating, device function, force acting on the device, and image distortion at 1.5 T. Clinical MR protocols and in vivo measurements yielded temperature changes 0.5°C. Older (manufactured before 2000) ICDs were damaged by the MR scans. Newer ICD systems and most pacemakers, however, were not. The maximal force acting on newer devices was 100 g. Modern (manufactured after 2000) ICD systems were implanted in dogs (n18), and after 4 weeks, 3- to 4-hour MR scans were performed (n15). No device dysfunction occurred. ...
AimsThe aim of this study was to evaluate the accuracy of multidetector computed tomographic angi... more AimsThe aim of this study was to evaluate the accuracy of multidetector computed tomographic angiography (MDCTA) for detecting hepatic artery complications after liver transplantation.
To prospectively determine whether mechanical behavior of left ventricular wall segments that con... more To prospectively determine whether mechanical behavior of left ventricular wall segments that contain different degrees of scar tissue and are located at different distances from the interface between infarcted and noninfarcted myocardial tissue can help predict inducibility of monomorphic ventricular tachycardia (VT) in patients with ischemic cardiomyopathy. This HIPAA-compliant study was institutional review board approved; written informed consent was obtained from all patients. Forty-six patients (36 men, 10 women; mean age +/- standard deviation, 61.6 years +/- 11.9) with prior myocardial infarction (MI) and left ventricular dysfunction were referred for defibrillator implantation and underwent an electrophysiologic examination and tagged contrast-enhanced magnetic resonance (MR) imaging. Peak circumferential shortening strain (Ecc) and time to peak Ecc were measured in 12 segments from short-axis sections. Remote, adjacent, and border zones were defined according to increasing proximity to the MI. Patients in whom monomorphic VT could be induced (ie, inducible patients) were considered positive for inducibility. Relationships between inducibility of monomorphic VT, peak Ecc, and time to peak Ecc were analyzed with one-way analysis of variance and Bonferroni test. Inducible patients had more infarcted and border zone sectors and a shorter time to peak Ecc than did noninducible patients in the border zone and adjacent and infarcted regions (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001). Peak Ecc in the border zone of inducible patients (-11.42% +/- 0.46 [standard error]) was greater than that in noninducible patients (-10.18% +/- 0.38; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .05). Ratio of Ecc in border zone and in remote regions was greater (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .05) in inducible patients than in noninducible patients (1.31 +/- 0.27 vs 0.64 +/- 0.13, respectively). Enhanced border zone function defined as greater Ecc and earlier time to peak Ecc showed positive correlation to VT inducibility in patients with prior MI and left ventricular dysfunction.
To fully characterize beam-hardening effects caused by iodinated contrast medium in the left vent... more To fully characterize beam-hardening effects caused by iodinated contrast medium in the left ventricular (LV) cavity and aorta in the assessment of myocardial perfusion at computed tomography (CT) and to validate a beam-hardening artifact correction algorithm that considers fluid-filled vessels and chambers important sources of beam hardening. The Johns Hopkins University animal care and use committee approved all procedures. An anatomically correct LV and myocardial phantom to characterize beam-hardening artifacts was designed. Following validation in the phantom, the beam-hardening correction (BHC) algorithm was applied to 256-detector row dynamic volume CT images in a canine ischemia model (n = 5) during adenosine stress, and the effect of beam hardening was determined by comparing regional dynamic volume CT perfusion metrics (myocardial upslope normalized by maximum LV blood pool attenuation) with microsphere-derived myocardial blood flow (MBF). A paired Student t test was used to compare continuous variables from the same subject but under different conditions, while linear regression analysis was performed to estimate the slope and statistical significance of the relationship between CT-derived perfusion metrics and microsphere-derived MBF. Beam-hardening artifacts were successfully reproduced in phantom studies and were eliminated with the BHC algorithm. The correlation coefficient of CT-derived perfusion metrics and microsphere-derived MBF improved from 0.60 to 0.74 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; .05) following correction in the animal model. Beam-hardening artifacts confound dynamic volume CT assessment of myocardial perfusion. Application of the BHC algorithm is helpful for improving accuracy of myocardial perfusion at dynamic volume CT.
The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has no... more The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has not been well established. We conducted a multicenter study to examine the accuracy of 64-row, 0.5-mm multidetector CT angiography as compared with conventional coronary angiography in patients with suspected coronary artery disease. Nine centers enrolled patients who underwent calcium scoring and multidetector CT angiography before conventional coronary angiography. In 291 patients with calcium scores of 600 or less, segments 1.5 mm or more in diameter were analyzed by means of CT and conventional angiography at independent core laboratories. Stenoses of 50% or more were considered obstructive. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of conventional angiography and subsequent revascularization status, whereas disease severity was assessed with the use of the modified Duke Coronary Artery Disease Index. A total of 56% of patients had obstructive coronary artery disease. The patient-based diagnostic accuracy of quantitative CT angiography for detecting or ruling out stenoses of 50% or more according to conventional angiography revealed an AUC of 0.93 (95% confidence interval [CI], 0.90 to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90% (95% CI, 83 to 94), a positive predictive value of 91% (95% CI, 86 to 95), and a negative predictive value of 83% (95% CI, 75 to 89). CT angiography was similar to conventional angiography in its ability to identify patients who subsequently underwent revascularization: the AUC was 0.84 (95% CI, 0.79 to 0.88) for multidetector CT angiography and 0.82 (95% CI, 0.77 to 0.86) for conventional angiography. A per-vessel analysis of 866 vessels yielded an AUC of 0.91 (95% CI, 0.88 to 0.93). Disease severity ascertained by CT and conventional angiography was well correlated (r=0.81; 95% CI, 0.76 to 0.84). Two patients had important reactions to contrast medium after CT angiography. Multidetector CT angiography accurately identifies the presence and severity of obstructive coronary artery disease and subsequent revascularization in symptomatic patients. The negative and positive predictive values indicate that multidetector CT angiography cannot replace conventional coronary angiography at present. (ClinicalTrials.gov number, NCT00738218.)
Background-MRI has the potential to visualize radiofrequency ablations (RFA), which have become t... more Background-MRI has the potential to visualize radiofrequency ablations (RFA), which have become the preferred treatment strategy for many arrhythmias. However, MRI patterns after RFA have not been well investigated.
The design and application of a two-wire electrophysiology (EP) catheter that simultaneously reco... more The design and application of a two-wire electrophysiology (EP) catheter that simultaneously records the intracardiac electrogram and receives the MR signal for active catheter tracking is described. The catheter acts as a long loop receiver, allowing for visualization of the entire catheter length while simultaneously behaving as a traditional two-wire EP catheter, allowing for intracardiac electrogram recording and ablation. The application of the device is demonstrated by simultaneously tracking the catheter and recording the intracardiac electrogram in canine models using 7 and 10 frame/sec real-time imaging sequences. Using solely MR imaging, the entire catheter was visualized and guided from the jugular vein into the cardiac chambers, where the intracardiac electrogram was recorded. By combining several functions in a single, simple structure, the excellent tissue contrast and functional imaging capabilities of MR can be used to improve the efficacy of EP interventions. This catheter will facilitate MR-guided interventions and demonstrates the design of multifunctional interventional devices for use in MRI. Magn Reson Med 47: 594 -600, 2002.
International Journal of Cardiovascular Imaging, 2009
Multidetector computed tomography (MDCT) using 64 detectors is widely used for cardiac imaging in... more Multidetector computed tomography (MDCT) using 64 detectors is widely used for cardiac imaging in the clinical setting. Despite promising results, 64-slice MDCT has important limitations for cardiac applications related to detector coverage, which leads to longer scan times, image artifacts, increased radiation and the need for higher contrast doses. The advent of wide or full cardiac coverage with 256- or
Journal of the American College of Cardiology, Jan 7, 2004
The goal of this study was to determine the magnitude and mechanisms of hemodynamic improvement o... more The goal of this study was to determine the magnitude and mechanisms of hemodynamic improvement of an automated, load-distributing band device (AutoPulse, Revivant Corp., Sunnyvale, California) compared with conventional cardiopulmonary resuscitation (C-CPR). Improved blood flow during cardiopulmonary resuscitation (CPR) enhances survival from cardiac arrest. AutoPulse CPR (A-CPR) and C-CPR were performed on 30 pigs (16 +/- 4 kg) 1 min after induction of ventricular fibrillation. Aortic and right atrial pressures were measured with micromanometers. Regional flows were measured with microspheres; A-CPR and C-CPR were performed with 20% anterior-posterior chest compression, with (n = 10) and without (n = 10) epinephrine. A pressure transducer was advanced down the airways during chest compressions (n = 10), and magnetic resonance imaging (MRI) was performed. AutoPulse CPR improved coronary perfusion pressure (CPP) (aortic - right atrial pressure) without epinephrine (A-CPR 21 +/- 8 mm...
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2015
Impaired catecholamine handling in the viable infarct border zone may play an important role in v... more Impaired catecholamine handling in the viable infarct border zone may play an important role in ventricular remodeling and lethal arrhythmia. We sought to get further biologic insights into cardiac sympathetic neuronal pathology after myocardial infarction, using multiple tomographic imaging techniques. In a porcine model of myocardial infarction (n = 13), PET and MR imaging were performed after 4-6 wk and integrated with electrophysiologic testing and postmortem histology. PET with the physiologic neurotransmitter (11)C-epinephrine, which is sensitive to metabolic degradation unless it is stored and protected in neuronal vesicles, identified a defect exceeding the perfusion defect (defined by (13)N-ammonia; defect size in all animals, 42 ± 12 vs. 35% ± 12% of left ventricle, P < 0.001). In a subgroup of 7 animals, defect of the metabolically resistant catecholamine (11)C-hydroxyephedrine was smaller than epinephrine (41 ± 8 vs. 47% ± 6% of left ventricle, P = 0.004), whereas def...
We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial per... more We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial permeability transition (MPT), was present in a translational swine model of heart failure with preserved ejection fraction (HFpEF). Cyclophilin D is a key component of the MPT pore, therefore, the purpose of this study was to test the efficacy of a novel cyclosporine (CsA) dosing scheme as a therapeutic alternative for HFpEF. Computed tomography (CT), two-dimensional speckle tracking two-dimensional speckle tracking (2DST), and invasive hemodynamics were used to evaluate cardiac function. CT imaging showed 14 weeks of CsA treatment caused eccentric myocardial remodeling (contrasting concentric remodeling in untreated HF animals) and elevated systemic pressures. 2DST detected left ventricular (LV) mechanics associated with systolic and diastolic dysfunction prior to the onset of significantly increased LV end diastolic pressure including: (1) decreased systolic apical rotation rate, longitudinal displacement, and longitudinal/radial/circumferential strain; (2) decreased early diastolic untwisting and longitudinal strain rate; and (3) increased late diastolic radial/circumferential mitral strain rate. LV mechanics associated with systolic and diastolic impairment was enhanced to a greater extent than seen in untreated HF animals following CsA treatment. In conclusion, CsA treatment accelerated the development of heart failure, including dilatory LV remodeling and impaired systolic and diastolic mechanics. Although our findings do not support CsA as a viable therapy for HFpEF, 2DST was effective in differentiating between progressive gradations of developing HF and detecting diastolic impairment prior to the development of overt diastolic dysfunction.
Journal of Interventional Cardiac Electrophysiology, 2004
Introduction: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly b... more Introduction: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly being selected based on anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures, we evaluated whether stereotactic catheter guidance might facilitate anatomical catheter navigation and RFA to the great vessels, the fossa ovalis and the left atrium (LA).
Heart rhythm : the official journal of the Heart Rhythm Society, 2014
Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ... more Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ventricular (LV) decompensation suffer from nearly 50% early mortality. Whether cardiac resynchronization therapy (CRT) improves hemodynamic status in this condition is unknown. We tested CRT in this setting by using a canine model of delayed lateral wall (LW) activation combined with 2 hours of coronary artery occlusion-reperfusion. This study aimed to evaluate the acute hemodynamic effects of CRT during and immediately after MI. Adult dogs (n = 8) underwent open-chest 2-hour mid-left anterior descending artery occlusion followed by 1-hour reperfusion. Four pacing modes were compared: right atrial pacing, pseudo-left bundle block (right ventricular pacing), and CRT with the LV lead positioned at either the LW (LW-CRT) or the peri-infarct zone (peri-infarct zone-CRT). Continuous LV pressure-volume data, regional segment length, and proximal left anterior descending flow rates were record...
Heart failure constitutes a major health problem in USA and Europe. Angiotensin converting enzyme... more Heart failure constitutes a major health problem in USA and Europe. Angiotensin converting enzyme inhibitors and _ blockers were shown to reduce morbidity and mortality in patients with CHF. Yet, their effectiveness is limited. A significant number of patients with heart failure manifest myocardial conduction abnormalities. Conduction abnormalities, especially in the form of left bundle branch block (LBBB) may be
Background-Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 m... more Background-Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 major factors: (1) low defibrillation success rates and (2) persistent post-countershock myocardial dysfunction. Biphasic (BP) waveforms may prove capable of favorably modifying these limitations. However, they have not been rigorously tested against monophasic (MP) waveforms in clinical models of external defibrillation, particularly where rescue from prolonged VF is the general rule. Methods and Results-We randomized 26 dogs to external countershocks with either MP or BP waveforms.
Background—QRS duration is commonly used to select heart failure patients for cardiac resynchroni... more Background—QRS duration is commonly used to select heart failure patients for cardiac resynchronization therapy (CRT). However, not all patients respond to CRT, and recent data suggest that direct assessments of mechanical dyssynchrony may better predict chronic response. Echo-Doppler methods are being used increasingly, but these principally rely on longitudinal motion (ll). It is unknown whether this analysis yields qualitative and/or
Journal of Nuclear Cardiology - J NUCLEAR CARDIOLOGY, 2010
Cardiovascular computed tomography (CT) is one of the most impressive advances in the non-invasiv... more Cardiovascular computed tomography (CT) is one of the most impressive advances in the non-invasive diagnosis of cardiovascular disease in the last decade. Going beyond coronary calcium scoring, cardiovascular CT is capable of identifying calcified and non-calcified plaque, percent stenosis, cardiac structure and morphology, and left ventricular systolic function. The abilities to detect subclinical and obstructive atherosclerosis and exclude disease with high diagnostic certainty are its greatest attributes. Single-center and multi-center studies in various cohorts have established that CT coronary angiography (CTA) is an accurate non-invasive test for determining percent stenosis which can be performed with low radiation dose. 1-7 However, it is important to point out that coronary CTA is an anatomical test that does not provide important physiological data. In fact, the value of CTA for predicting the presence of myocardial ischemia is limited. 8-10 While coronary CTA has an excellent negative predictive value, it is more limited in determining the significance of stenoses in patients with disease. Thus, caution needs to be exercised when adopting cardiac CT clinically. The importance of coronary physiology for diagnosis, prognosis, and guidance of therapies must not be ignored.
Background—MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as... more Background—MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MRI. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. Our aim was to determine whether these modern systems can be used in an MR environment. Methods and Results—We tested in vitro and in vivo lead heating, device function, force acting on the device, and image distortion at 1.5 T. Clinical MR protocols and in vivo measurements yielded temperature changes 0.5°C. Older (manufactured before 2000) ICDs were damaged by the MR scans. Newer ICD systems and most pacemakers, however, were not. The maximal force acting on newer devices was 100 g. Modern (manufactured after 2000) ICD systems were implanted in dogs (n18), and after 4 weeks, 3- to 4-hour MR scans were performed (n15). No device dysfunction occurred. ...
AimsThe aim of this study was to evaluate the accuracy of multidetector computed tomographic angi... more AimsThe aim of this study was to evaluate the accuracy of multidetector computed tomographic angiography (MDCTA) for detecting hepatic artery complications after liver transplantation.
To prospectively determine whether mechanical behavior of left ventricular wall segments that con... more To prospectively determine whether mechanical behavior of left ventricular wall segments that contain different degrees of scar tissue and are located at different distances from the interface between infarcted and noninfarcted myocardial tissue can help predict inducibility of monomorphic ventricular tachycardia (VT) in patients with ischemic cardiomyopathy. This HIPAA-compliant study was institutional review board approved; written informed consent was obtained from all patients. Forty-six patients (36 men, 10 women; mean age +/- standard deviation, 61.6 years +/- 11.9) with prior myocardial infarction (MI) and left ventricular dysfunction were referred for defibrillator implantation and underwent an electrophysiologic examination and tagged contrast-enhanced magnetic resonance (MR) imaging. Peak circumferential shortening strain (Ecc) and time to peak Ecc were measured in 12 segments from short-axis sections. Remote, adjacent, and border zones were defined according to increasing proximity to the MI. Patients in whom monomorphic VT could be induced (ie, inducible patients) were considered positive for inducibility. Relationships between inducibility of monomorphic VT, peak Ecc, and time to peak Ecc were analyzed with one-way analysis of variance and Bonferroni test. Inducible patients had more infarcted and border zone sectors and a shorter time to peak Ecc than did noninducible patients in the border zone and adjacent and infarcted regions (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001). Peak Ecc in the border zone of inducible patients (-11.42% +/- 0.46 [standard error]) was greater than that in noninducible patients (-10.18% +/- 0.38; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .05). Ratio of Ecc in border zone and in remote regions was greater (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .05) in inducible patients than in noninducible patients (1.31 +/- 0.27 vs 0.64 +/- 0.13, respectively). Enhanced border zone function defined as greater Ecc and earlier time to peak Ecc showed positive correlation to VT inducibility in patients with prior MI and left ventricular dysfunction.
To fully characterize beam-hardening effects caused by iodinated contrast medium in the left vent... more To fully characterize beam-hardening effects caused by iodinated contrast medium in the left ventricular (LV) cavity and aorta in the assessment of myocardial perfusion at computed tomography (CT) and to validate a beam-hardening artifact correction algorithm that considers fluid-filled vessels and chambers important sources of beam hardening. The Johns Hopkins University animal care and use committee approved all procedures. An anatomically correct LV and myocardial phantom to characterize beam-hardening artifacts was designed. Following validation in the phantom, the beam-hardening correction (BHC) algorithm was applied to 256-detector row dynamic volume CT images in a canine ischemia model (n = 5) during adenosine stress, and the effect of beam hardening was determined by comparing regional dynamic volume CT perfusion metrics (myocardial upslope normalized by maximum LV blood pool attenuation) with microsphere-derived myocardial blood flow (MBF). A paired Student t test was used to compare continuous variables from the same subject but under different conditions, while linear regression analysis was performed to estimate the slope and statistical significance of the relationship between CT-derived perfusion metrics and microsphere-derived MBF. Beam-hardening artifacts were successfully reproduced in phantom studies and were eliminated with the BHC algorithm. The correlation coefficient of CT-derived perfusion metrics and microsphere-derived MBF improved from 0.60 to 0.74 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; .05) following correction in the animal model. Beam-hardening artifacts confound dynamic volume CT assessment of myocardial perfusion. Application of the BHC algorithm is helpful for improving accuracy of myocardial perfusion at dynamic volume CT.
The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has no... more The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has not been well established. We conducted a multicenter study to examine the accuracy of 64-row, 0.5-mm multidetector CT angiography as compared with conventional coronary angiography in patients with suspected coronary artery disease. Nine centers enrolled patients who underwent calcium scoring and multidetector CT angiography before conventional coronary angiography. In 291 patients with calcium scores of 600 or less, segments 1.5 mm or more in diameter were analyzed by means of CT and conventional angiography at independent core laboratories. Stenoses of 50% or more were considered obstructive. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of conventional angiography and subsequent revascularization status, whereas disease severity was assessed with the use of the modified Duke Coronary Artery Disease Index. A total of 56% of patients had obstructive coronary artery disease. The patient-based diagnostic accuracy of quantitative CT angiography for detecting or ruling out stenoses of 50% or more according to conventional angiography revealed an AUC of 0.93 (95% confidence interval [CI], 0.90 to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90% (95% CI, 83 to 94), a positive predictive value of 91% (95% CI, 86 to 95), and a negative predictive value of 83% (95% CI, 75 to 89). CT angiography was similar to conventional angiography in its ability to identify patients who subsequently underwent revascularization: the AUC was 0.84 (95% CI, 0.79 to 0.88) for multidetector CT angiography and 0.82 (95% CI, 0.77 to 0.86) for conventional angiography. A per-vessel analysis of 866 vessels yielded an AUC of 0.91 (95% CI, 0.88 to 0.93). Disease severity ascertained by CT and conventional angiography was well correlated (r=0.81; 95% CI, 0.76 to 0.84). Two patients had important reactions to contrast medium after CT angiography. Multidetector CT angiography accurately identifies the presence and severity of obstructive coronary artery disease and subsequent revascularization in symptomatic patients. The negative and positive predictive values indicate that multidetector CT angiography cannot replace conventional coronary angiography at present. (ClinicalTrials.gov number, NCT00738218.)
Uploads
Papers by Albert Lardo