Preliminary Clinical Experience with the First Dual Chamber Pacemaker Defibrillator

The lack of specificity of VT detection is a significant shortcoming of current ICDs. In a French multicenter study, 18 patients underwent implantation of the Defender 9001 (ELA Medical), an ICD utilizing dual chamber pacing and arrhythmia detection. Over a mean follow-up period of 7.1 ± 4.5 months, 176 tachycardia episodes recorded in the device memory were analyzed, and physician diagnosis was compared with that by the device. All 122 VT/VF episodes were correctly diagnosed, as were 51 of 53 supraventricular tachyarrhythmias. Two episodes of AF with rapid regular ventricular rates were treated as VT, and a third episode, treated as VT, could not be diagnosed with certainty. A dual chamber pacemaker defibrillator offers improved diagnostic specificity without loss of sensitivity, in addition to the hemodynamic benefit of dual chamber pacing. (PACE 1997;20     

Update on Percutaneous Mechanical Mitral Commissurotomy

A reusable metallic valvotomy device has been developed with the goals of improving the results of percutaneous mitral valvotomy and increasing the cost-effectiveness of the procedure. The device consists of a detachable and reusable metallic dilator with two articulated bars screwed at the distal end of a catheter. Using transseptal catheterization, the device is placed across the valve over a traction guidewire and then opened gradually by means of pliers up to a maximum of 40 mm. To date, the device was used in 168 patients with a broad spectrum of mitral valve disease. The procedure was successful in 95% of cases and resulted in an increase in mitral valve area from 1.01 ± 0.8 to 2.20 ± 0.7 cm². No increase in mitral regurgitation was noted in 87% of cases. Bilateral splitting of the commissures was observed in 89%. Complications included the following: 2 severe mitral regurgitations (one requiring surgery), 1 pericardial tamponade, 1 transient cerebrovascular embolic event. The maximum number of consecutive patients treated with the same device was 35. The results obtained are at least comparable to those of current balloon techniques and confirm the possibility of safe multiple reuses of the device after sterilization.     

Underdetection of Ventricular Tachycardia Using a 40 ms Stability Criterion: Effect of Antiarrhythmic Therapy

Inappropriate shocks can complicate cardioverter defibrillator therapy. Among solutions proposed to avoid oversensing are algorithms to reduce inappropriate detection of atrial fibrillation (AF) or sinus tachycardia. In patients not on antiarrythmic drugs, an interval stability criterion of 40 ms has been validated with the Medtronic PCD to discriminate ventricular tachycardia (VT) from AF. With this algorithm, VT is considered stable if no interval varies from one of the three preceding in tervals by more than 40 ms. If an interval does not fulfill this criterion, the VT event counter is reset to zero. The aim of this study was to investigate the incidence of underdetection when this criterion is ap plied in patients treated with antiarrhythmic drugs. We studied 132 sustained monomorphic VTs induced in 42 patients during 101 electrophysiological studies (EPS). EPS were performed without treatment (group I. 24 patients, 44 VTs); on Class Ia drug (group II, 17 patients, 24 VTs); Class Ic drug (group III, 22 patients, 39 VTs); or sotalol (group IV, 17 patients, 25 VTs). The endocardial electrogram of all VT episodes was digitized and the stability algorithm was applied. The reset arrhythmias were distributed among no delay, small, moderate (<10 s) and important (>15 s) delay in VT detection. The relation be tween drug use and reset was analyzed. Beset was found in 86 (65%) of induced VTs. No difference in heart rate or induction mode was shown between reset and nonreset VTs. There was a significative asso ciation between drag use and reset probability (Chi² significantly different, P < 0.05). In patients treated with Class Ic drugs, the probability of finding an important delay in VT detection was 12.5% versus 0% in nontreated patients or in patients treated with sotalol. We conclude that a stability criterion of 40 ms is probably safe in nontreated patients but should be used with caution in patients treated with antiarrhythmics, especially in the presence of Class Ic drags.     

Update on Interventions in Renal Artery Stenosis

Noninvasive techniques such as ultrasound and renal scanning have improved the frequency of detection of renal artery stenosis in patients with arterial hypertension, renal insufficiency, or multivascular disease. The results of conventional balloon angioplasty on nonostial renal artery stenoses caused by fibromuscular dysplasia or atherosclerosis showed a high recurrence rate and a moderate impact on the management of hypertension. In patients with ostial lesions, the results of angioplasty were disappointing with low initial success rates and a high rate of restenosis. Other limitations of balloon angioplasty include initial failure or suboptimal result, occluding dissection, and short- or mid-term restenosis. The immediate procedural results of renal artery stenting are excellent, with a low complication rate and satisfactory restenosis rate. Long-term effects on renal function and blood pressure seem to be good. Systematic stent placement is indicated for ostial stenosis. For nonostial lesions, the indication for stent placement may be reserved for residual stenosis or dissection. The indication for a stent would probably be more liberal in cases of bilateral lesions or lesions in a solitary kidney. Multicenter studies probably will be needed to assess the indications and benefits obtained in different clinical and anatomical situations.     

Interatrial Conduction in Patients Undergoing AV Stimulation: Effects of Increasing Right Atrial Stimulation Rate

To evaluate the frequency of spontaneous or rate dependent interatrial blocks, the interatrial conduction time (IACT) was studied on 100 consecutive patients (mean age 78.3 ±7.8 years) during a transvenous dual chamber pacemaker implant. The spontaneous interatrial conduction time (SIACT) was measured from the intrinsic deflection (ID) of the unipolar right atrial signal to the ID of the left atrial signal recorded in a bipoiar way by an esophageal lead. The paced interatrial conduction time (PIACT) was measured from the stimulus artifact to the left atrial ID, when the atrium was paced at a slightly higher rate than the spontaneous rate and during incremental atrial pacing. From these measurements, the maximum increase ofPIACT (MIPIACT) was deduced. In this elderly population, the PIACT was similar (117 ± 26.9 msec) to the data in the literature. However, there were large interindividual variations that were also found in SIACT. We found a close correlation between SIACT and PIACT (P < 0.0001). PIACT was on average 50 msec longer than SIACT. SIACT increased with age (P < 0.03). The MIPIACT was 15.3 ± 15.2 msec. In the majority of patients, the MIPIACT was > 10 msec, and even reached 90 msec in one patient. MIPIACT was longer in patients with a PIACT exceeding 110 msec (P < 0.004). Based on IACT alone, the AV interval must be lengthened on average by 50 msec when changing from atrial tracking-ventricular pacing to atrial pacing-ventricular pacing, but large individual differences must be kept in mind. Elderly people should probably have a longer AV delay.     

Percutaneous Implantation of Aortic Valve Prosthesis in Patients with Calcific Aortic Stenosis: Technical Advances, Clinical Results and Future Strategies

To date, one third of patients with symptomatic aortic stenosis are not operated on because of advanced age, depressed left ventricular function, or comorbidities. Whereas balloon aortic valvuloplasty can be used as a palliative treatment in this population, the hemodynamic and clinical benefits of the procedure are only temporary. With the goal of offering to this subset of patients a nonsurgical therapeutic option with improved results and longer term positive outcomes, we developed a percutaneous implantable bioprosthetic heart valve able to be inserted within the native diseased aortic valve using cardiac catheterization techniques. The first human implant was performed by our group in April 2002 using the antegrade transeptal approach. Since then, we have implanted the valve on compassionate basis in a series of nonsurgical elderly patients with end-stage aortic stenosis and multiple comorbidities, all declined by cardiac surgeons for valve replacement. This article describes the technical improvements of the device and implantation protocols, provides clinical results of the first series of patients, and outlines strategies for future development of the percutaneous heart valve.