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D Schwartzman

Publications and source records attributed to D Schwartzman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Narrowing of the superior vena cava-right atrium junction during radiofrequency catheter ablation for inappropriate sinus tachycardia: analysis with intracardiac echocardiography.

OBJECTIVES: The study explored the potential for tissue swelling and venous occlusion during radiofrequency (RF) catheter ablation procedures using intracardiac echocardiography (ICE). BACKGROUND: Transient superior vena cava occlusion has been reported following catheter ablation procedures for inappropriate sinus tachycardia (IST). Presumably, venous occlusion could occur owing to thrombus formation or tissue swelling with resultant narrowing of the superior vena cava-right atrial (SVC-RA) junction. METHODS: Intracardiac echocardiography (9 MHz) was used to guide ablation catheter position and for continuous monitoring during RF application in 13 ablation procedures in 10 patients with IST. The SVC-RA junction was measured prior to and following ablation. Successful ablation was marked by abrupt reduction in the sinus rate and a change to a superiorly directed p-wave axis. RESULTS: Eleven of 13 procedures were successful, requiring 29 +/- 20 RF lesions. Prior to the delivery of RF lesions, the SVC-RA junction measured 16.4 +/- 2.9 mm. With RF delivery, local and circumferential swelling was observed, causing progressive reduction in the diameter of the SVC-RA junction to 12.6 +/- 3.3 mm (24% reduction, p = 0.0001). A reduction in SVC-RA orifice diameter of > or = 30% compared to baseline was observed in five patients. CONCLUSIONS: The delivery of multiple RF ablation lesions, often necessary for cure of IST, can cause considerable atrial swelling and resultant narrowing of the SVC-RA junction. Smaller venous structures, such as the coronary sinus and the pulmonary veins, would also be expected to be vulnerable to this complication. Thus, ICE imaging may be helpful in preventing excessive tissue swelling leading to venous occlusion during catheter ablation procedures.

Adult↗
PubMed1999

Electrical impedance properties of normal and chronically infarcted left ventricular myocardium.

BACKGROUND: Previous reports have disclosed that a significant difference exists between the electrical impedance properties of healthy and chronically infarcted ventricular myocardium. PURPOSE: To assess the potential utility of electrical impedance as the basis for mapping in chronically infarcted left ventricular myocardium. Specifically: (1) to delineate electrical impedance properties of healthy and chronically infarcted ventricular myocardium, with special emphasis on the infarction border zone; (2) to correlate impedance properties with tissue histology; (3) to correlate impedance properties with electrogram amplitude and duration; (4) To demonstrate that endocardial impedance can be measured effectively in vivo using an electrode mounted on a catheter inserted percutaneously. METHODS: An ovine model of chronic left ventricular infarction was utilized. Sites of healthy myocardium, densely infarcted myocardium and the infarction border zone were investigated. Bulk impedance was measured in vitro using capacitor cell, four-electrode and unipolar techniques. Epicardial and endocardial impedances were measured in vivo using four-electrode and unipolar techniques. Impedance was measured at multiple frequencies. Electrographic amplitude, duration and amplitude/duration ratio were measured using bipolar electrograms during sinus rhythm. Quantitation of tissue content of myocytes, collagen, elastin and neurovascular elements was performed. RESULTS: Densely infarcted myocardial impedance was significantly lower than healthy myocardium. Impedance gradually decreased in the border zone transitioning between healthy myocardium and dense infarction. Decreasing impedance correlated with a decrease in tissue myocyte content. The magnitude of the difference in impedance between densely infarcted and healthy myocardium increased as the measurement frequency decreased. Healthy myocardium exhibited a marked frequency dependence in its impedance properties; this phenomenon was not observed in densely infarcted myocardium. There was a direct association between impedance and both electrogram amplitude and amplitude/duration ratio. There was an inverse association between impedance and electrogram duration. Endocardial impedance, measured in vivo using a electrode catheter inserted percutaneously, was demonstrated to distinguish between healthy and infarcted myocardium. CONCLUSIONS: The electrical impedance properties of healthy and infarcted left ventricular myocardium differ markedly. The properties of the infarction border zone are intermediate between healthy and infarcted myocardium. Impedance may be a useful assay of cardiac tissue content and adaptable for cardiac mapping in vivo. Condensed Abstract. To delineate the electrical impedance properties of healthy and chronically infarcted left ventricular myocardium emphasizing the infarction border zone, impedance was measured in chronically infarcted ovine hearts. Densely infarcted myocardial impedance was significantly lower than healthy myocardium. Impedance gradually decreased in the infarction border zone in transition between healthy myocardium and dense infarction. This correlated with a decreasing myocyte content. The magnitude of the difference in impedance between densely infarcted and healthy myocardium increased as measurement frequency decreased. There was a direct association between impedance and electrogram characteristics. Endocardial impedance, measured in vivo using an electrode catheter inserted percutaneously, distinguished between healthy and infarcted myocardium

Action Potentials↗
PubMed1999

Antidromic reciprocating tachycardia in patients with paraseptal accessory pathways: importance of critical delay in the reentry circuit.

Previous studies in patients with antidromic reciprocating tachycardia (ART) have observed a critical anatomic requirement (> 4 cm) between an antegrade bypass tract limb and a retrograde AV nodal limb. We report two patients with ART utilizing a paraseptal accessory pathway. In both cases, a critical degree of slow conduction within the circuit provides unusual electrophysiologic substrate to overcome the expected anatomical constraints.

Adult↗
PubMed1998

Imaging technique and clinical utility for electrophysiologic procedures of lower frequency (9 MHz) intracardiac echocardiography.

Intracardiac echocardiography using a new 9-MHz ultrasound catheter was performed in 30 patients undergoing percutaneous catheter mapping and radiofrequency ablation of a tachyarrhythmia, because the imaging capabilities with this intracardiac echocardiographic catheter permit detailed identification of normal and abnormal cardiac anatomy with improved imaging depth. Intracardiac echocardiography is of significant clinical utility during ablation for guiding interatrial septal puncture, assessing placement and contact of mapping/ablation catheters, monitoring ablation lesion morphologic changes, and diagnosing procedure-related complications.

Adult↗
PubMed1998

Efficacy of radiofrequency catheter ablation for ventricular tachycardia in healed myocardial infarction.

Radiofrequency catheter ablation has been useful in the treatment of ventricular tachycardia (VT) in selected patients with healed myocardial infarction. Previous studies have demonstrated success rates of 60% to 96% for targeted VT morphologies; however, these studies included patients only after they have had successful mapping procedures and have received radiofrequency lesions. All patients referred for VT ablation from July 1992 to November 1996 were included in this analysis on an intention-to-treat basis. Ninety-five procedures were performed in 66 patients for 77 distinct presentations with tolerated, sustained VT. Fifty-five procedures were successful (58%) and 40 procedures failed. Reasons for procedural failure included failed radiofrequency application despite adequate VT mapping (21 procedures), no tolerated VT induced (12), and aborted procedures due to complications or technical difficulties (7). Fifty-five patients (71%) eventually had a successful VT ablation, although 10 required > 1 procedure. This analysis revealed factors that contribute to failure of VT ablation procedures in addition to inadequate mapping and lesion formation. Procedural difficulties, particularly the inability to induce tolerated VT, frequently prevent successful catheter ablation in patients who present with tolerated, sustained VT.

Aged↗
PubMed1998

Autonomic nervous system activity and the spontaneous initiation of ventricular tachycardia. ESVEM Investigators. Electrophysiologic Study Versus Electrocardiographic Monitoring Trial.

OBJECTIVES: We hypothesized that neurohormonal activity contributes to the initiation of sustained ventricular tachycardia (VT) as reflected in indices of heart rate variability (HRV). BACKGROUND: Autonomic nervous system activity participates in experimental arrhythmias but clinical studies have been inconsistent. METHODS: Holter electrocardiograms from 53 patients with VT were analyzed. Heart rate variability indices were determined over 5 and 15 min and 24 h and examined for changes before the onset of VT. Heart rate variability indices in the frequency domain included ultra low frequency power (FP) (ULFP): 0-0.0033 Hz; very low FP (VLFP): 0.0033-0.04 Hz; low FP (LFP): 0.04-0.15 Hz; high FP (HFP): 0.15-0.4 Hz; total power (TP); normalized LFP (LFPn); normalized HFP (HFPn), and the ratio: LFP/HFP. RESULTS: Heart rate variability indices were severely diminished: TP: 12,009+/-11,076 ms2; ULFP: 10,087+/-9,565 ms2; VLFP: 1,416+/-1,571 ms2; LFP: 544+/-620 ms2; HFP: 161+/-176 ms2, and LFP/HFP: 3.68+/-2.83. Heart rate increased before VT (80.4+/-17.3 to 85.3+/-17.4 bpm, p < 0.001). Several HRV variables declined 30 min before VT compared to 24-h values (VLFP: -5.89+/-17.81%, p = 0.031; LFP: -5.23+/-14.3%, p = 0.003; HFP: -4.35+/-13.7%, p = 0.04). LFPn and the LFP/HFP ratio decreased significantly before the onset of VT (-17.7+/-46.9%, p = 0.035 and -8.24+/-38.8%, p = 0.037, respectively), whereas HFPn increased slightly (4.29+/-29.9%, p = 0.097). CONCLUSIONS: Heart rate rose, whereas LFP, LFPn and LFP/HFP fell before the onset of VT. This pattern of changes could be explained by a rise in sympathetic activity and saturation of the HRV signal resulting in dissociation of the average and rhythmical effects of sympathetic activity. These findings suggest that alterations in autonomic activity contributed to arrhythmogenesis in this group of patients.

Aged↗
PubMed1998

Recording of pacing stimulus artifacts by endovascular defibrillation lead systems: comparison of true and integrated bipolar circuits.

BACKGROUND: The occurrence ICD undersensing of ventricular fibrillation due to the presence of a pacing stimulus artifact (PSA) is in part related to the amplitude of the artifact recorded on the ICD rate sensing circuit. There is little comparative data regarding PSA amplitude recorded by commercial ICD rate-sensing circuits. PURPOSE: To compare PSA amplitude recorded by commercial endovascular defibrillation leads utilizing integrated or true bipolar sensing circuits. METHODS: Nineteen large (60-120 kg) pigs were utilized. Two different commercial endovascular defibrillation leads were evaluated, each with its distal tip located at the right ventricular apex: (1) Medtronic Transvene; and (2) CPI Endotak. Three different rate-sensing circuits were evaluated: (1) Transvene true bipolar (tip-ring); (2) Transvene integrated bipolar (tip-coil); and (3) Endotak integrated bipolar (tip-coil). Using a separate pacing lead located at the left ventricular apex (n = 19 animals) or right ventricular outflow tract (n = 10 animals), pacing was performed at a pulse width of 0.5 milliseconds at outputs of 1.5, 5 and 10 volts. PSA amplitude was recorded at each output by each circuit. RESULTS: During pacing from the left ventricular apex, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.6 +/- 0.1 mV at 1.5 volts, 2.0 +/- 0.5 mV at 5 volts, 3.7 +/- 0.8 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.4 +/- 0.3 mV at 1.5 volts, 3.8 +/- 0.7 mV at 5 volts, 4.1 +/- 0.8 mV at 10 volts) or the Endotak integrated circuit (1.8 +/- 0.4 mV at 1.5 volts, 4.2 +/- 1.0 mV at 5 volts, 6.3 +/- 1.8 mV at 10 volts). During pacing from the right ventricular outflow tract, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.7 +/- 0.1 mV at 1.5 volts, 1.7 +/- 0.4 mV at 5 volts, 4.0 +/- 0.7 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.1 +/- 0.4 mV at 1.5 volts, 3.9 +/- 1.2 mV at 5 volts, 7.5 +/- 1.8 mV at 10 volts) or the Endotak integrated circuit (1.6 +/- 0.7 mV at 1.5 volts, 4.3 +/- 1.7 mV at 5 volts, 7.5 +/- 2.6 mV at 10 volts). For both pacing sites, the PSA amplitude recorded by the two integrated circuits was not significantly different. CONCLUSIONS: For a given pacing output voltage, PSA amplitude recorded by commercial endovascular rate sensing/defibrillation leads is greater when the sensing circuit is integrated than when it is true bipolar. These data may be helpful in planning ICD implantation in patients with previously implanted permanent pacemakers.

Animals↗
PubMed1998

Anatomy-guided linear atrial lesions for radiofrequency catheter ablation of atrial fibrillation.

The surgical atrial maze procedure has provided proof that atrial fibrillation can be cured by performing atrial incisions based on anatomical and electrophysiological principles. Preliminary reports of attempts at radiofrequency catheter ablation of atrial fibrillation utilizing an anatomy-based "linear incision" method have shown the feasibility of the method. However, postprocedural atrial fibrillation recurrence has been common and in addition new, uniform tachycardias have developed in some patients. Both of these outcomes may be in part due to incomplete or inconsistent lesion deployment. This article details the use of the CARTO system for deploying anatomy guided linear atrial lesions for the purpose of curing atrial fibrillation. The procedure is comprised of three phases, which are discussed in detail: (1) baseline map; (2) lesion deployment and; (3) lesion assessment. Using a single standard ablation electrode, lesions can be deployed safely, and complete lesions can be confirmed. Paradigms for right and left atrial incisions are proposed.

Animals↗
PubMed1997

Lower frequency (5 MHZ) intracardiac echocardiography in a large swine model: imaging views and research applications.

Our previous investigation indicated that, in the 50-114-kg weight range, the swine model provides transeosophageal echocardiographic normal values for cardiac structures comparable to those found in human adults. Intracardiac echocardiographic imaging using a 12.5-MHz ultrasound catheter is limited, due to ultrasonic attenuation. Transesophageal echocardiographic imaging of the right heart is also limited with its anterior anatomic location. To further study the utility of intracardiac imaging, we placed a 5-MHz (30 Fr) multiplane transducer at the junction of the superior vena cava and right atrium, in the right atrium and right ventricle in 8 closed-chest swine (weight 129 +/- 61 kg). In each animal, complete whole heart imaging was obtained, with tomographic views including the cardiac 4-chamber, right atrium, right ventricle and outflow, left atrium and ventricle, and basal great vessels. Major intracardiac anatomic landmarks (i.e., crista terminalis, right atrial appendage, coronary sinus orifice, interatrial septum, tricuspid valve, right ventricular outflow, pulmonary veins, mitral valve and left ventricular papillary muscles) were visualized in every swine. Thus, this 5-MHz multiplane transducer, as a prototype for a steerable low-frequency intracardiac ultrasound catheter, improved both whole heart and individual cardiac structure imaging from a single intracardiac location. Further technological development and refinement is needed for routine use in research and clinical imaging practice.

Animals↗
PubMed1997

Repetitive monomorphic tachycardia from the left ventricular outflow tract: electrocardiographic patterns consistent with a left ventricular site of origin.

OBJECTIVES: This study sought to characterize the electrocardiographic patterns predictive of left ventricular sites of origin of repetitive monomorphic ventricular tachycardia (RMVT). BACKGROUND: RMVT typically arises from the right ventricular outflow tract (RVOT) in patients without structural heart disease. The incidence of left ventricular sites of origin in this syndrome is unknown. METHODS: Detailed endocardial mapping of the RVOT was performed in 33 consecutive patients with RMVT during attempted radiofrequency ablation. Left ventricular mapping was also performed if pace maps obtained from the RVOT did not reproduce the configuration of the induced tachycardia. RESULTS: Pace maps identical in configuration to the induced tachycardia were obtained from the RVOT in 29 of 33 patients. Application of radiofrequency energy at sites guided by pace mapping resulted in elimination of RMVT in 24 (83%) of 29 patients. In four patients (12%), pace maps obtained from the RVOT did not match the induced tachycardia. All four patients had a QRS configuration during RMVT with precordial R wave transitions at or before lead V2. In two patients, RMVT was mapped to the mediosuperior aspect of the mitral valve annulus, near the left fibrous trigone; catheter ablation at that site was successful in both. In two patients, RMVT was mapped to the basal aspect of the superior left ventricular septum. Catheter ablation was not attempted because His bundle deflections were recorded from this site during sinus rhythm. CONCLUSIONS: RMVT can arise from the outflow tract of both the right and left ventricles. RMVTs with a precordial R wave transition at or before lead V2 are consistent with a left ventricular origin.

Adult↗
PubMed1997

Characterization of the excitable gap in human type I atrial flutter.

OBJECTIVES: We sought to characterize the excitable gap of the reentrant circuit in atrial flutter. BACKGROUND: The electrophysiologic substrate of typical atrial flutter has not been well characterized. Specifically, it is not known whether the properties of the tricuspid valve isthmus differ from those of the remainder of the circuit. METHODS: Resetting was performed from two sites within the circuit: proximal (site A) and distal (site B) to the isthmus in 14 patients with type I atrial flutter. Resetting response patterns and the location where interval-dependent conduction slowing occurred were assessed. RESULTS: Some duration of a flat resetting response (mean +/- SD 40.1 +/- 20.9 ms, 16 +/- 8% of the cycle length) was observed in 13 of 14 patients; 1 patient had a purely increasing response. During the increasing portion of the resetting curve, interval-dependent conduction delay most commonly occurred in the isthmus. In most cases, the resetting response was similar at both sites. In three patients, the resetting response differed significantly between the two sites; this finding suggests that paced beats may transiently change conduction within the circuit or the circuit path, or both. CONCLUSIONS: Some duration of a flat resetting response was observed in most cases of type I atrial flutter, signifying a fully excitable gap in all portions of the circuit. The isthmus represents the portion of the circuit most vulnerable to interval-dependent conduction delay at short coupling intervals.

Action Potentials↗
PubMed1997

Right ventricular radiofrequency ablation of ventricular tachycardia after myocardial infarction.

Radiofrequency transcatheter ablation of ventricular tachycardia in the setting of a prior myocardial infarction is typically performed with application of energy to the left ventricular endocardium. In this article, two cases are described in which successful radiofrequency transcatheter ablation of ventricular tachycardia occurred with energy delivery to the right ventricular septum after failed ablation attempts from the left ventricle. Both patients had tachycardias with a left bundle branch block morphology and markedly presystolic activity recorded from the right ventricular septum. Right ventricular septal activation mapping during ventricular tachycardia should be performed in patients with left bundle branch block tachycardia morphology and coronary artery disease to maximize efficacy of the catheter ablation procedure.

Aged↗
PubMed1997

Does the initial presentation of patients with implantable defibrillator influence the outcome?

The influence of the clinical presentation on the long-term outcome in 213 consecutive patients with ICDs, ECG storage capability, and nonthoracotomy leads, was analyzed. Sixty-six patients presented with cardiac arrest (CA), 81 patients with hemodynamically stable VT, and 66 patients with syncope (SY). Patient characteristics were: mean age CA 62, VT 61, SY 61 years; mean ejection fraction CA 31%, VT 29%, SY 30%; coronary artery disease CA 71%, VT 71%, SY 64% (all P > 0.05 Fisher's exact test); female gender CA 40%, VT 14%, SY 19% (CA vs VT and SY, P < 0.005); inducibility by programmed stimulation CA 50%, VT 84%, SY 61% (VT vs CA and SY, P < 0.001, CA vs SY, P > 0.05). During a mean follow-up of 14.5 months, 29 patients died: CA 12%, VT 14%, SY 9% (P > 0.05). Comparing Kaplan-Meier curves, no difference in the time course of overall mortality was found (log-rank P > 0.05). In the CA, VT, and SY groups, 543, 1,630, and 189 ICD therapies (including antitachycardia pacing, low energy cardioversion, and defibrillation) were observed, respectively. Actuarial analysis showed a shorter interval between implantation and first ICD therapy for VT versus CA and SY (log-rank P < 0.005). Patients presenting with VT experienced earlier and more frequent ICD therapies than patients with CA or SY independent of age, ejection fraction, and heart disease. No difference in overall mortality and time course of fatal events was observed among the three groups.

Actuarial Analysis↗