Resynchronization therapy optimization by intracardiac impedance.

AIMS: For successful cardiac resynchronization therapy (CRT), an optimization of left ventricular (LV) lead position and stimulation timing is required. The feasibility of optimizing LV lead position, atrioventricular delay (AVd), and interventricular delay (VVd) in CRT using intracardiac impedance measurement was evaluated. METHODS AND RESULTS: Heart failure patients (n = 14, NYHA 13×III, 1×II, ejection fraction: 26 ± 6%, QRS: 165 ± 30 ms) were stimulated by AAI and biventricular (DDD-BiV) pacing in turn. Left ventricular lead site, AVd, and VVd were varied. An external pacemaker measured impedance, and a micromanometer catheter measured LV and aortic pressure. Left ventricular dP/dt(max), pulse pressure (PP), stroke volume (SV), end-systolic impedance (ESZ), and stroke impedance (SZ) were determined. Optimization results achieved by maximum increase in PP, SV, SZ, or ESZ were compared with the reference method (dP/dt(max) increase). Left ventricular lead site variation resulted in a mean optimal dP/dt(max) benefit of 18.2%. Lead site selection by SZ/PP/SV showed benefits of 17.4/17.9/17.2%, respectively. Atrioventricular delay optimization increased the optimal benefit to 22.1%, the methods ESZ/PP/SV achieved 20.1/20.8/19.4%. Interventricular delay optimization resulted in a benefit of 19.1/19.4/19.9% (SZ/PP/SV) with an optimum of 21.8%. The achieved benefit did not differ significantly between impedance, SV, and PP methods. A significant correlation between AVd values selected by dP/dt(max) and by the other methods was observed (r = 0.75/0.67/0.60 for ESZ/PP/SV). CONCLUSION: The feasibility of optimizing LV lead site, AVd, and VVd by intracardiac impedance has been demonstrated for CRT patients with a similar performance as using SV and PP. Application of intracardiac impedance for automatic implant-based CRT optimization appears to be within reach.

Intracardiac impedance monitors stroke volume in resynchronization therapy patients.

AIMS: Monitoring of haemodynamic parameters or surrogate parameters of the left ventricle is especially important for patients under cardiac resynchronization therapy (CRT). Intracardiac impedance reflects left ventricular (LV) volume changes well in animal models. Since it is unknown whether this also holds in humans with heart failure (HF), we examined the correlation of LV intracardiac impedance with haemodynamic parameters in CRT patients for different positions of the LV lead. METHODS AND RESULTS: In 14 HF patients with non-ischaemic cardiomyopathy (four female, age 70 +/- 6 years, NYHA 2.9 +/- 0.3, EF 26 +/- 6%), one or two suitable implantation sites for the LV lead were selected. Following atrial, right ventricular, and LV catheter positioning, a micro-manometer catheter was placed in the ascending aorta. Surface ECG, impedance, and aortic pressure were recorded during graded overdrive bi-ventricular pacing in DDD mode. The correlation between impedance and stroke volume (SV) or pulse pressure (PP) changes was compared for different LV lead positions. In total, 20 overdrive pacing tests were performed at six different LV lead positions. Strong correlations were found between stroke impedance (SZ) and SV (R = 0.82 +/- 0.16) as well as between SZ and PP (R = 0.81 +/- 0.16) without significant influence of LV lead position. CONCLUSION: In HF patients, a strong correlation between changes in intracardiac impedance and LV SV was found. Typical LV lead implant positions have been tested and all appear to be suitable for this method of LV volume monitoring.

[Troubleshooting in Patients with Implanted Pacemaker and ICD]. / Troubleshooting bei Patienten mit Herzschrittmacher und ICD.

Because of the growing number of implanted cardiac pacemakers and defibrillators and the ever-increasing complexity of these devices a fundamental knowledge of device malfunctions is of utmost importance even for the non-cardiology physician. Apart from hardware problems such as device infection, lead fracture or dislocation, basic knowledge of the pacemaker sensing and pacing algorithms is also necessary in order to judge the stimulation behavior in different clinical settings. With this respect, there are specific problems for antibradycardia and resynchronizing pacemakers as well as implantable defibrillators. This article gives an overview of the most common problems with cardiac pacemakers and defibrillators as well as the differential diagnostic and therapeutic management for the physician without specific training in arrhythmology.

Endocardial radiofrequency ablation for hypertrophic obstructive cardiomyopathy: acute results and 6 months' follow-up in 19 patients.

OBJECTIVES: The purpose of this study was to examine the efficacy and safety of endocardial radiofrequency ablation of septal hypertrophy (ERASH) for left ventricular outflow tract (LVOT) gradient reduction in hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Anatomic variability of the vessels supplying the obstructing septal bulge can limit the efficacy of transcoronary ablation of septal hypertrophy in HOCM. Previous studies showed that inducing a local contraction disorder without reducing septal mass results in effective gradient reduction. We examined an alternative endocardial approach to transcoronary ablation of septal hypertrophy by using ERASH. METHODS: Nineteen patients with HOCM were enrolled; in 9 patients, the left ventricular septum was ablated, and in 10 patients, the right ventricular septum was ablated. Follow-up examinations (echocardiography, 6-min walk test, bicycle ergometry) were performed 3 days and 6 months after ERASH. RESULTS: After 31.2 ± 10 radiofrequency pulses, a significant and sustained LVOT gradient reduction could be achieved (62% reduction of resting gradients and 60% reduction of provoked gradients, p = 0.0001). The 6-min walking distance increased significantly from 412.9 ± 129 m to 471.2 ± 139 m after 6 months, p = 0.019); and New York Heart Association functional class was improved from 3.0 ± 0.0 to 1.6 ± 0.7 (p = 0.0001). Complete atrioventricular block requiring permanent pacemaker implantation occurred in 4 patients (21%); 1 patient had cardiac tamponade. CONCLUSIONS: ERASH is a new therapeutic option in the treatment of HOCM, allowing significant and sustained reduction of the LVOT gradient as well as symptomatic improvement with acceptable safety by inducing a discrete septal contraction disorder. It may be suitable for patients not amenable to transcoronary ablation of septal hypertrophy or myectomy.

Predictors of complete heart block after transcoronary ablation of septal hypertrophy: results of a prospective electrophysiological investigation in 172 patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVES: This study analyzed changes in intracardiac conduction during transcoronary ablation of septal hypertrophy (TASH) to identify predictors for pacemaker dependency after TASH. BACKGROUND: Transcoronary ablation of septal hypertrophy is an accepted therapeutic option in hypertrophic obstructive cardiomyopathy (HOCM). However, atrioventricular conduction disorders, requiring permanent pacemaker implantation, remain a major adverse effect. METHODS: This study measured changes in intracardiac conduction in 172 consecutive patients during TASH by simultaneously recording electrophysiological parameters and correlated these parameters with the occurrence of complete heart block during continuous electrocardiographic monitoring for 8 days. RESULTS: Intraprocedural complete heart block occurred in 36 patients (20.1%) and was associated with a pre-existing bundle branch block (p = 0.010) or advanced age (p = 0.023). All patients with delayed complete heart block during follow-up (n = 15, 8.7%), occurring 1 to 6 days after TASH, showed lack of retrograde atrioventricular nodal conduction after TASH (p = 0.018). None of the patients with intact retrograde conduction after TASH developed delayed complete heart block. Further risk factors for delayed block were advanced age, intraprocedural complete heart block, and prolonged QRS duration before or after TASH (p < 0.05 for all). Permanent pacemaker implantation was performed in 20 patients. CONCLUSIONS: Measurement of intracardiac conduction during TASH improves the safety of the procedure by enabling identification of patients who are at risk of complete heart block after TASH. The duration of prophylactic temporary pacemaker backup should be prolonged up to day 6 after TASH in patients at increased risk (patients with retrograde atrioventricular block and at least 1 additional risk factor).

Transcoronary ablation of septal hypertrophy does not alter ICD intervention rates in high risk patients with hypertrophic obstructive cardiomyopathy.

INTRODUCTION: Transcoronary ablation of septal hypertrophy (TASH) is safe and effectively reduces the intraventricular gradient in patients with hypertrophic obstructive cardiomyopathy (HOCM). To analyze the potential of anti- and proarrhythmic effects of TASH, we studied the discharge rates of implanted cardioverter defibrillators (ICD) in patients with HOCM who are at a high risk for sudden cardiac death. METHODS: ICD and TASH were performed in 15 patients. Indications for ICD-implantation were secondary prevention in nine patients after resuscitation from cardiac arrest with documented ventricular fibrillation (n = 7) or sustained ventricular tachycardia (n = 2) and primary prevention in 6 patients with a family history of sudden deaths, nonsustained ventricular tachycardia, and/or syncope. All the patients had severe symptoms due to HOCM (NYHA functional class = 2.9). RESULTS: During a mean follow-up time of 41 +/- 22.7 months following the TASH procedure, 4 patients had episodes of appropriate discharges (8% per year). The discharge rate in the secondary prevention group was 10% per year and 5% in the group with primary prophylactic implants. Three patients died during follow-up (one each of pulmonary embolism, stroke, and sudden death). CONCLUSION: In conclusion, on the basis of ICD-discharge rates in HOCM-patients at high risk for sudden death, there is no evidence for an unfavorable arrhythmogenic effect of TASH. The efficacy of ICD treatment for the prevention of sudden cardiac death in HOCM could be confirmed, however, mortality is high in this cohort of hypertrophic cardiomyopathy patients.