Christopher M. Lowery

Implantable cardioverter-defibrillator shocks in patients with a left ventricular assist device

BACKGROUND Left ventricular assist device (LVAD) use is becoming increasingly common for patients with end-stage heart failure. However, the rate of implantable cardioverter-defibrillator (ICD) shocks and the effect of these shocks on outcomes in patients with LVADs remain unknown. METHODS Medical records were reviewed from patients with both an ICD and a LVAD from September 2000 to February 2009. The association between ICD shocks and survival while receiving device support was assessed using Cox proportional hazards modeling. RESULTS Thirty-three of 61 patients with a LVAD also had an ICD and form the basis of this report. The mean duration of LVAD support was 238 days. One or more ICD shocks were delivered to 14 patients (42%) with 8 (24%) receiving appropriate shocks for ventricular arrhythmias and 6 (18%) receiving inappropriate shocks. No patients received both appropriate and inappropriate shocks. When compared with receiving no ICD shock, receiving any ICD shock or an appropriate ICD shock were both associated with an increase in the risk of death (hazard ratio [HR] 4.5, 95% confidence interval [CI] 1.2 to 17.3, p = 0.027, and HR 5.3, 95% CI 1.3 to 22.6, p = 0.023, respectively); receipt of an inappropriate shock showed a non-significant trend for an increased risk of death (HR 3.2, 95% CI 0.7 to 16.1, p = 0.151). CONCLUSIONS ICD shocks are common after implantation of LVADs, with nearly equal numbers of appropriate and inappropriate shocks. ICD shocks are associated with higher mortality. Larger studies are needed for assessing the independent relationship of ICDs to a variety of clinical outcomes in patients with LVADs.

Effect of left ventricular assist device placement on preexisting implantable cardioverter-defibrillator leads.

BACKGROUND The left ventricular assist device (LVAD) is a therapy for patients with end-stage heart failure, many of whom have a preexisting implantable cardioverter-defibrillator (ICD). We investigated whether the implantation of a LVAD affects ICD function. METHODS AND RESULTS Patients implanted with a LVAD between September 2000 and February 2009 were studied. Right ventricular (RV), right atrial, and left ventricular lead impedance, sensing, and capture thresholds were recorded before and after LVAD placement and subsequent lead-related interventions were noted. Of the 61 patients receiving a LVAD, data were collected from 30 patients who had preexisting ICDs. Significant pre-post differences were noted for all RV lead parameters: sensing amplitude decreased from 9.2+/-3.1 to 5.7+/-3.6 millivolts (P < .001); impedance decreased from 479+/-118 to 418+/-94 ohms (P=.008); and threshold increased from 4.3+/-6.7 to 11.0+/-16.8 microjoules (P=.021). As a result of alterations in lead parameters, 4 patients (13%) required lead revisions and 6 patients (20%) required ICD testing. CONCLUSIONS Differences in ICD lead function were observed after LVAD placement resulting in clinically significant interventions. These data suggest that ICD interrogation be performed post-LVAD placement and that patients be counseled for the potential need for lead revisions and ICD testing when consented for a LVAD.

Endocardial Electrogram Characteristics of Epicardial Ventricular Arrhythmias

While most ventricular arrhythmias (VA) can be ablated successfully using an endocardial (endo) approach, epicardial (epi) mapping and ablation is sometimes required. There may be suggestive clues on the surface electrocardiogram; however, identification of an epi origin of VA with certainty remains problematic.

Sequential dual chamber extrastimulation: A novel pacing maneuver to identify the presence of a slowly conducting concealed accessory pathway

BACKGROUND Transient VA block can be created in the AV node (AVN) when an atrial extrastimulus is delivered at the AVN effective refractory period (ERP) due to anterograde concealed conduction. OBJECTIVE We hypothesized that ventricular stimulation during pacing-induced AVN refractoriness could identify concealed accessory pathways (APs) that remain hidden with standard maneuvers. METHODS Patients undergoing electrophysiological study for supraventricular tachycardia were screened for presence of an AP using standard pacing maneuvers and/or V pacing during adenosine infusion. The dual-chamber sequential extrastimulation maneuver consisted of an 8-beat drive train of simultaneous AV pacing at 600 msec, followed by an A2 delivered at AVN ERP, followed by a V2 delivered at the drive train cycle length (600 msec). Repeat drives were then performed with decrements of 10 msec for V2 until VA block was seen. Retrograde AVN and AP ERP were recorded with standard (V1, V2) and dual-chamber extrastimulation (A1/V1, A2, V2). Patients with an AP identified with standard pacing, manifest pre-excitation, or A ERP < AVN ERP were excluded. RESULTS Fourteen patients with and 19 patients without an AP were studied. In all patients with an AP, exclusive VA conduction over the AP, without fusion, was seen with the described pacing maneuver. In patients without an AP, retrograde AV nodal ERP was extended by a mean of 138 +/- 46 msec (range 50 to 210 msec) with the A2. Anterograde concealed conduction into the AP was also seen in some patients who showed AP conduction during standard V1V2 pacing (mean retrograde extension of ERP 12 +/- 8 msec, range 0 to 20 msec). CONCLUSION Dual-chamber sequential extrastimulation is a useful maneuver for identifying slowly conducting APs not revealed with standard pacing maneuvers because of an ERP and conduction time similar to the AVN. The maneuver uses anterograde concealed conduction to prolong AVN refractoriness much more than that of a concealed AP, thereby allowing the AP to become manifest with the V2.

Use of stored implanted cardiac defibrillator electrograms in catheter ablation of ventricular fibrillation.

Ventricular fibrillation (VF) can be abolished by targeting triggering ventricular ectopy, most often originating in the Purkinje network or right ventricular outflow tract (RVOT). This strategy relies upon the induction of premature ventricular complex (PVC) and/or VF. We sought to evaluate a VF ablation strategy that utilizes analysis of stored implantable cardioverter defibrillator (ICD) electrograms.

A Potential Para‐Hisian Pacing Pitfall

Para-Hisian pacing is a useful maneuver to identify the presence of a concealed septal pathway.1 To perform this maneuver, stimulation at a ventricular site near the bundle of His is delivered with varying pacing outputs. After capturing the His bundle, reduction in the pacing output will result in ventricular capture without His bundle capture, resulting in a wider paced complex width. The comparison in ventriculoatrial (VA) times between His capture and ventricular capture beats can identify the presence of a septal accessory pathway. We report a case where an unusual response to para-Hisian pacing occurred. In the figure below, there appears to be His capture with a measured VA time of 198 ms (Fig. 1, Panel A). Subsequently, there is a wider complex indicating loss of His capture and resultant ventricular capture with an identical VA time of 198 ms. This response is consistent with retrograde conduction over a septal accessory pathway. Because other pacing maneuvers failed to demonstrate the presence of an

P-Wave Rejection in a Transplanted Heart

Background: Heart block can occur at multiple levels in patients with prior cardiac transplant. This diagnosis is usually ascertained using the surface electrocardiogram.