Sensing lead failure in implantable defibrillators: a comparison of two commonly used leads.

INTRODUCTION: Despite major technological advances, structural problems in implantable cardioverter defibrillator (ICD) endocardial sensing leads remain a significant problem. There are two types of ICD sensing leads: (1) dedicated bipolar leads and (2) integrated lead systems that include defibrillation coils. The long-term performance of these two lead systems has not been directly compared. METHODS AND RESULTS: We prospectively examined the incidence of lead failure manifested by inappropriate arrhythmia detection in 247 consecutive patients undergoing abdominal ICD implant at a single center between 1991 and 1995. A total of 107 patients received BT-10 (dedicated bipolar) leads and 140 patients received Endotak (integrated bipolar) leads. Over a mean follow-up of 860 +/- 442 days, there were 19 (17.8%) lead failures with the BT-10 lead (261 to 1,505 days postimplant) compared with only 6 (4.3%; P < 0.01) with the Endotak lead (410 to 1,211 days postimplant). Lead failure was due to an insulation defect in all cases, with the problem occurring in the proximal lead (within the pulse generator pocket) in all but one case. Lead survival was significantly better with the Endotak lead (P = 0.015, risk ratio = 3.0, 95% confidence intervals 1.2 to 7.6). CONCLUSION: Late lead failure due to insulation defects in BT-10 sensing leads (causing inappropriate ICD activation) is a relatively common and progressive phenomenon, with difficulties becoming apparent as long as 4 years after implant. This problem is a likely cause of inappropriate shocks in patients with BT-10 leads. Implantation of a new sensing lead should be considered at the time of elective pulse generator replacement, even in the absence of demonstrable oversensing.

Diagnostic value of a pacemaker high rate episode counter when programming the ventricular tachycardia zone of an ICD.

A 72-year-old man with an ICD and a pacemaker was presented with an episode of sustained VT that accelerated to VF. The ICD failed to detect the event and deliver therapy, despite a VT apparently within the VT detection zone. The ICD detected the event after degeneration to VF and delivered appropriate therapy. The high rate event feature of the pacemaker was useful in determining proper function of the ICD along with optimal programming of VT detection.

Use of atrial and ventricular electrograms from a dual chamber implantable cardioverter defibrillator to elucidate a complex dysrhythmia.

Stored intracardiac electrograms provided by third-generation ICDs have proved their use in the analysis of the mechanism of tachydysrhythmic events. There are cases in which the analysis of ventricular electrograms is insufficient for the elucidation of certain dysrhythmias. The availability of atrial electrograms provided by dual chamber ICDs improves the diagnostic capability of electrogram analysis and could prove most useful especially in complex dysrhythmias.

Papillary muscle rupture after chordal sparing mitral valve replacement.

Complete papillary muscle rupture is a catastrophic complication of acute myocardial infarction which usually leads to acute severe mitral regurgitation requiring urgent or emergent surgery. A case in which this complication occurred after chordal sparing mitral valve replacement is described. The severed papillary muscle was removed surgically. The incidence and natural history of papillary muscle rupture occurring after chordal sparing mitral valve replacement for ischemic mitral insufficiency is not known.

Calculation of the aortic valve gradient from the left ventricular-femoral and aortic-femoral pairs of pressure waveforms.

Accurate measurement of the transaortic gradient is important in the invasive assessment of the significance of aortic stenosis. The mean gradient obtained from simultaneous left ventricular and aortic pressure recordings is the gold standard, but requires two central catheters. We hypothesized that a gradient calculated by subtracting the aortofemoral from the ventriculofemoral gradient would reproduce the ventriculoaortic gradient. In 24 patients sequential recordings of the aortofemoral, ventriculofemoral, and ventriculoaortic pressures pairs were obtained. The calculated ventriculoaortic gradient was obtained by subtracting the aortofemoral gradient from the ventriculofemoral gradient. Both of these gradients were measured by computer, using a systolic ejection period between the crossovers of the upslope and downslope of the left ventricular waveform with the femoral waveform. The ventriculoaortic gradient calculated using this technique correlated closely with the gradient measured by two central catheters (R = 0.99). This technique is accurate and does not require two central catheters.