Matthias Manz

A Single Intravenous Dose of Ivabradine, a Novel If Inhibitor, Lowers Heart Rate but Does Not Depress Left Ventricular Function in Patients with Left Ventricular Dysfunction

This randomized, single-blind, placebo-controlled study investigated the effect of ivabradine, a novel heart rate-lowering agent, on echocardiographic indices of left ventricular (LV) systolic function in patients with regional (coronary artery disease) or global (cardiomyopathy) LV dysfunction. Patients were randomized on an unequal basis to receive ivabradine 0.25 mg/kg (n = 31) or placebo (n = 13) by intravenous infusion. Resting heart rate was reduced by a mean of 17.6 ± 4.7% with ivabradine and 1.5 ± 5.8% with placebo. The mean maximum decrease in LV ejection fraction was 0.2% with ivabradine and 1.7% with placebo. Fractional shortening and stroke volume were also fully preserved after ivabradine administration. Thus, a single intravenous dose of ivabradine produced a substantial reduction in resting heart rate without affecting LV function in patients with regional or global LV dysfunction.

Patient Acceptance of the Implantable Cardioverter Defibrillator in Ventricular Tachyarrhythmias

Besides surgical problems, recipierifs of implantable cardioverter defibrillators (ICDs) are faced with psychological and social adjustments. Successful ICD therapy is influenced by the patients’ perceived concerns regarding device, discharge, changes in life style, and complications. In order to assess patients’ acceptance of the ICD, the psychological profile of 57 consecutive patients was evaluated using a specifically designed questionnaire and the State Trait Anxiety Inventory (STAI). The results showed that 20 patients staled fear of ICD discharge, 12 patients revealed physical discomfort due to the device, and limited quality‐of‐life occurred in 8 patients. Fifty‐five of 57 patients answered that it was worth having an ICD device implanted, 30 (53%) patients returned to active life, and 56 (98%) would advise another patient to undergo implantation if necessary. Overall, there was only a slight, but insignificant, decrease in the level of anxiety within the total patient population after ICD implantation. However, a comparison of two subgroups indicated that the state of anxiety was significantly higher in patients < 50 years of age as well as in patients having received > 5 shocks versus those > 50 years of age and having experienced < 5 shocks. In general, the acceptance of the ICD as a tool in managing life‐threatening ventricular tachyarrhythmias is high. Besides the increased survival rate, quality‐of‐life and patient acceptance are important criteria for successful ICD therapy.

Effects of chronic amiodarone therapy on defibrillation threshold

In a prospective and parallel, randomized study, the long-term stability of epicardial defibrillation threshold was evaluated in 22 patients, using a patch-patch lead configuration at the time of implantation and generator replacement. The concomitant antiarrhythmic drug treatment consisted of either mexiletine (720 mg/day) or amiodarone (400 mg/day) and was administered to patients in a randomized and parallel manner. During a mean follow-up of 24 +/- 6 months, the defibrillation threshold increased significantly from 14.3 +/- 2.8 to 17.9 +/- 5.3 J (p < 0.05) for the entire patient group. The increase in the chronic defibrillation threshold was due to a marked increase in defibrillation energy needs in the subgroup of patients receiving amiodarone. Whereas no significant change in the defibrillation threshold was documented in the subgroup of patients receiving mexiletine, the mean defibrillation threshold increased from 14.1 +/- 3.0 to 20.9 +/- 5.4 J (p < 0.001) in those receiving amiodarone. In all patients with increased defibrillation thresholds, reevaluation showed a reduction in the defibrillation threshold after discontinuation of antiarrhythmic drug therapy. The only variable associated with an increase in the chronic defibrillation threshold was amiodarone treatment. These findings suggest that the defibrillation threshold should be measured at each generator replacement and in case of a change in antiarrhythmic drug treatment. In particular, if amiodarone treatment is initiated, it is recommended that the defibrillation threshold should be reevaluated to ensure an adequate margin of safety.

Color-coded Doppler imaging of the vena contracta as a basis for quantification of pure mitral regurgitation

The narrowest central flow region of a jet is defined as the vena contracta. This term is applied also to the contracted zone of the Doppler color flow image of a jet at its passage through an incompetent mitral valve. The clinical applicability of measuring the size of the vena contracta by transthoracic color-coded Doppler echocardiography for estimating the severity of mitral regurgitation (MR) was evaluated. In 78 of 82 patients with angiographically proved MR, a coherent flow image across the valve was visualized. The maximal diameter in the apical long-axis view was considered as a representative value for the size of the vena contracta. In comparison with the maximal left atrial velocity pixel area, this parameter revealed higher correlations to the angiographic degree of MR and to the regurgitant volume (r = 0.94 vs 0.72, and 0.83 vs 0.71, respectively). The highest positive and negative predictive accuracies for differentiating mild-to-moderate from severe MR were determined for a diameter of 6.5 mm (88 and 96%, respectively). Because the vena contracta is directly related to the severity of MR, it is concluded that it is helpful to use this parameter instead of the maximal velocity pixel area for semiquantitative grading.

Effects of nuclear magnetic resonance imaging on cardiac pacemakers.

Patients with cardiac pacemakers are currently restricted from nuclear magnetic resonance imaging (MRI), The aim of the study was to analyze the influence of MBI on new generation pacemakers. Tests were performed using a phantom model with seven dual chamber and two single chamber systems in a 0.5 Tesla MRI scanner. Monitoring by telemetry and oscillography were used during the standard clinical scan sequences as well as a pacemaker inquiry after each sequence. Spin echo, gradient echo, and fast field echo sequences were performed with the following stimulation modes: VVI, VVIR, VOO, DDD, DDDR, and DOO. On entering the static magnetic field, the reed switch was activated followed by asynchronous stimulation. The subsequent scan showed no influence on the stimulation function nor on the pacemaker program. Event counter function remained intact. Pacemakers with automatic mode switching to demand pacing or programmed inactivotion of the reed switch were triggered in the dual chamber mode and were inhibited in the one chamber mode during the scan. Alterations of pacemaker program or rapid pacing were not observed. MRI scan could induce voltage as high as intracardiac signals, but the stimulation threshold of the heart was not reached. Thus, pacemakers should be programmed in the asynchronous mode during scan to avoid inhibition and trigger mechanism.

Patient acceptance of implantable cardioverter defibrillator devices: Changing attitudes

Clinical experience suggests that the implantable cardioverter defibrillator (ICD) can reduce sudden cardiac death and total mortality in patients with malignant ventricular arrhythmia who meet the selection criteria for implantation. In addition to surgical problems, patients are faced with psychological and social adjustments. Patient acceptance for such therapy is marked by perceived concerns regarding device discharge, life-style alterations, and complications. We included 57 patients with ICDs in a study of their acceptance of the device. Results of a specially designed questionnaire (state-trait personality inventory) showed that 47 of 57 patients felt that their symptoms improved with the ICD system, 32 were constantly aware of the device, and 24 patients acclimated to the ICD system within less than 2 months. With respect to the need for battery replacement, only 27 patients requested a repeat electrophysiologic evaluation, 20 patients stated fear of ICD discharges, 12 patients revealed physical discomfort from the device, and limited quality of life occurred in eight patients. Fifty-five of 57 patients answered that it was worth having an ICD device implanted, 30 (53%) patients returned to active life, and 56 (98%) would advise another patient to have an ICD implantation if necessary. In conclusion, in general, the acceptance of the ICD as a tool for management of life-threatening ventricular tachyarrhythmias is very high. Quality of life and patient acceptance are important criteria for successful ICD therapy in addition to the improved survival rate.

Failure of an implantable cardioverter-defibrillator to redetect ventricular fibrillation in patients with a nonthoracotomy lead system.

BACKGROUND Shock delivery of an implantable defibrillator may cause a change in the amplitude of endocardial electrograms and impair the detection of ventricular fibrillation. Thus, the effects of shock discharges on the amplitude of endocardial electrograms were evaluated in five patients undergoing implantation of a cardioverter-defibrillator in combination with a new nonthoracotomy lead system. METHODS AND RESULTS At implant, bipolar endocardial electrograms were recorded before each shock application, during ventricular fibrillation, during redetection of ventricular fibrillation in case the applied shock was ineffective, and at intervals of 5, 10, 20, 30, 60, and 120 seconds after each shock delivery. The amplitude of the endocardial electrograms decreased from 10.5 +/- 3.8 mV during sinus rhythm to 6.3 +/- 1.9 mV during initial ventricular fibrillation and declined to 2.2 +/- 1.3 mV during redetection of ventricular fibrillation. After successful termination, the following bipolar electrograms could be obtained at the predetermined intervals: 1.9 +/- 1.2 mV, 3.1 +/- 1.8 mV, 4.5 +/- 1.9 mV, 6.5 +/- 2.9 mV, 9.5 +/- 3.3 mV, and 10.4 +/- 3.8 mV. At predischarge testing, failure of redetection of ventricular fibrillation could be documented in two patients, requiring rescue external defibrillation in both cases to restore sinus rhythm. CONCLUSIONS These findings demonstrate that the implantable cardioverter-defibrillator did not ensure reliable redetection of ventricular fibrillation in patients using the implanted nonthoracotomy lead system. Thus, the potential risk of sudden cardiac death may persist in these patients despite defibrillator therapy.

Incidence of ICD Lead Related Complications During Long‐Term Follow‐Up: Comparison of Epicardial and Endocardial Electrode Systems

The aim of this study was to evaluate the longterm stability of epicardial and endocardial lead systems for third‐generation cardioverter defibrillators (ICDs) and to assess the usefulness of diagnostic tools. One hundred forty patients with 61 epicardial (43.6%) and 79 nonthoracotomy systems (56.4%) were followed for 2 5 ± 19 months. A total of 18 (12.9%) lead related complications were documented. Complications of epicardial systems were detected in 10 patients (16.4%) during a follow‐up time of 36 ± 8 months: crinkling of patch electrodes in 6 patients (9.8%), insulation breakage of sensing electrodes in 2 patients (3.3%), and adapter defect in 2 patients (3.3%). Eight of the patients (10.1%) with transvenous‐subcutaneous systems had lead related complications during a 13 ± 6 months follow‐up: fracture of the subcutaneous patch lead in 2 patients (2.5%), dislodgment of the right ventricular lead in 2 patients (2.5%), dislodgment of the superior vena cava lead in 2 patients (2.5%), insulation breakage of sensing electrodes in 1 patient (1.3%), and connector defect in 1 patient (1.3%). There was no significant difference in the incidence of lead related complications between epicardial and endocardial systems (P > 0.05). Fractures, dislodgments, and crinklings were documented within the first 8 ± 5 months by regular chest X ray. Defects of insulation, adapter, or connector were detected 22 ± 10 months after implantation and were associated with delivery of multiple inappropriate ICD therapies. An operative lead revision was indicated for 4 epicardial (6.6%) and 6 endocardial (7.6%) lead systems. Conclusions: Endocardial lead systems offer a similar long‐term stability as compared to epicardial had systems. Chest X ray is the most useful tool to detect lead fracture, dislodgment. and patch crinkling. Marker recordings or real‐time electrograms have not been helpful in this series to identify patients with suspected lead defects prior to the experience of inappropriate ICD discharges.

Complications of pacemaker-defibrillator devices: Diagnosis and management

Treatment of resuscitated patients with implantable cardioverter defibrillators has become increasingly more common as a method for the prevention of sudden cardiac death. Major complications such as perioperative death (incidence 2% to 8%), infection (2% to 11%); and lead-related problems (3% to 27%) have been described in previous trials. In our experience with 140 patients, problems were related to leads (n = 11), the device (n = 2), pacing (n = 1), sensing (n = 13), and defibrillation function (n = 5). Additional problems that occurred during the perioperative period included infection (n = 11), hematoma, and seroma (n = 2). Thrombus formation along endocardial leads was observed in 13 of 62 (21%) patients. Different arrhythmias (n = 10), such as sinus tachycardia, atrial fibrillation, and nonsustained, slow or incessant ventricular tachycardia with shock delivery, were also detected. Surgical management (predominantly for the major problems) was used in 31 (48%) patients, drug treatment in 25 (39%), and reprogramming of the device in 24 (38%) patients. All of these problems can result in an increase in mortality rates. This article provides an overview of the complications of cardioverter defibrillator treatment and is based on both published data and our series.

Interactions between drugs and devices: Experimental and clinical studies

It is important to understand the potential interactions between the implantable cardioverter defibrillator (ICD) and antiarrhythmic therapy in patients who receive pharmacologic therapy as an adjunct to ICD therapy. In our cohort of 101 patients, antiarrhythmic agents were prescribed in 67% of the patients during long-term therapy for the following reasons: to suppress ventricular tachycardia/ventricular fibrillation episodes (50%), to lower the rate of ventricular tachycardia (19%), to prevent supraventricular tachyarrhythmia (21%), and for other reasons (10%). The potential influence of antiarrhythmic drugs on the defibrillation threshold (DFT) is the most important issue. In animal studies lidocaine increased the DFT in a dose-dependent manner. Quinidine, procainamide, propafenone, and flecainide did not affect the DFT or, in some cases, led to a small increase. Sotalol even decreased the energy requirements for internal defibrillation. In a prospective investigation we were able to document a significant increase of DFT (from 14.1 + 3.0 to 20.9 + 5.4 J, p < 0.001) by the use of amiodarone (400 mg/day), whereas this effect was not found in patients who received mexiletine (720 mg/day). In conclusion, the DFT or the safety margin for defibrillation should be known before antiarrhythmic agents are administered to patients with an ICD. In case of a small safety margin, the DFT should be reassessed after antiarrhythmic drug therapy is begun.