Iatrogenic pacemaker-induced ventricular arrhythmia: a case report

Background

Minimizing right ventricular (RV) pacing to reduce the progression of heart failure is an established practice. Proprietary algorithms to reduce unnecessary RV pacing have been incorporated into both simple and complex cardiac pacemaker devices, for reducing the possibility of heart failure and arrhythmias.

Case summary

We present a case of a 43-year-old male implanted with a dual-chamber primary prevention implantable cardioverter-defibrillator (AUTOGEN EL, Boston Scientific) for sudden cardiac death. At the time of implant, the patient had hypertrophic cardiomyopathy with mild left ventricular (LV) systolic impairment, and sinus rhythm with intact atrioventricular (AV) conduction. The patient developed progression of his disease with symptoms (dyspnoea) and LV impairment. This led to a decision to activate the minimal RV pacing algorithm (RYTHMIQ™). A deterioration in AV conduction caused intrinsic ventricular beats to fall in the atrial blanking period, and subsequent VVI backup pacing resulted in R on T pacing. This induced ventricular arrhythmia. RYTHMIQ™ was subsequently deactivated, and the patient has had no further device-induced arrhythmias.

Discussion

Numerous studies have demonstrated the adverse effect of RV pacing on LV function. Minimizing RV pacing is, therefore, encouraged in individuals with intact AV conduction. However, underlying conduction abnormalities must be assessed prior to activating algorithms designed to minimize RV pacing. This case demonstrates the importance of careful intracardiac electrogram interpretation and individual case-based device programming, to avoid device-induced complications.

Atrial septal pacing in small dogs: a pilot study

OBJECTIVE

To determine the feasibility of atrial septal pacing via a delivery catheter-guided small non-retracting helix pacing lead.

ANIMALS

Six healthy beagles (8.3-12.9 kg).

METHODS

Using single plane fluoroscopic guidance, Medtronic(®) 3830 SelectSecure leads were connected to the atrial septum via Medtronic® Attain Select® II standard 90 Left Heart delivery catheter. Pacing threshold and lead impedance were measured at implantation. The Wenckebach point was tested via atrial pacing up to 220 paced pulses per minute (ppm). Thoracic radiographs were performed following implantation to identify the lead position, and repeated at 24 h, 1 month, and 3 months post-operatively.

RESULTS

Macro-lead dislodgement occurred in two dogs at 24 h and in three dogs at one-month post-implantation. Lead impedance, measured at the time of implantation, ranged from 583 to 1421 Ω. The Wenckebach point was >220 ppm in four of the six dogs. The remaining two dogs had Wenckebach points of 120 and 190 ppm.

CONCLUSIONS

This pilot study suggests the selected implantation technique and lead system were inadequate for secure placement in the atrial septum of these dogs. The possible reasons for inadequate stability include unsuitable lead design for this location, inadequate lead slack at the time of implantation and inadequate seating of the lead as evidenced by low impedance at the time of implantation. Other implantation techniques and/or pacing leads should be investigated to determine the optimal way of pacing the atria in small breed dogs that are prone to sinus node dysfunction.

Characterization of B-cell subpopulations in patients with chronic rhinosinusitis

BACKGROUND

Recent research suggest that B and plasma cells may play an important role in the pathogenesis of chronic rhinosinusitis with nasal polyposis (CRSwNP). The purpose of this study was to subcharacterize the B cell response in the sinus mucosa of control and CRS patients.

METHODS

Representative tissue samples and peripheral blood samples were obtained from controls, CRS without nasal polyps (CRSsNP) and CRSwNP. Using single-cell suspension flow cytometry these samples were analyzed for overall and stage-specific B and plasma cell percentages.

RESULTS

Both atopic and nonatopic CRSwNP patients showed an increase in local numbers of naive, active, and memory B cells compared to controls. CRSsNP patients only showed local elevations of naive B cells. Plasma cells were only significantly elevated in the sinus tissue of atopic CRSwNP patients. These local tissue increases did not correlate with increased numbers of circulating B cells.

CONCLUSION

This study provides further evidence of an important role of B cells in CRSwNP patients. The local increase appears to be independent of a systemic response.

Current concepts in pacing 2010-2011: the right and wrong way to pace

OPINION STATEMENT

Over five decades have passed since the first permanent cardiac pacemakers were introduced into clinical medicine. Evolving technology and falling costs have demanded adaptation to clinical practice and implantation trends and, with the advent of evidenced-based medicine, the specific roles and benefits of individual pacemaker technologies have never been so carefully scrutinized. Pacing mode choice continues to be a subject of great controversy, and there are great regional variations in practice. We believe that single chamber atrial pacing use (AAI/R) has become an anachronism that should generally be abandoned (obviously with rare exceptional cases) and be replaced by dual chamber pacemakers (DDD/R) equipped with modern pacing algorithms that minimize patient exposure to ventricular pacing. Also, in patients with atrioventricular (AV) block, randomized clinical trials have failed to show improvement in clinically relevant outcomes such as mortality, stroke, and heart failure, particularly in the elderly, which has led some to advocate that DDD/R devices should never be offered to elderly AV block patients. However, we believe that the elderly, like the young, come in many "shapes and sizes" and individualized medicine compels us to consider each pacemaker candidate as unique. Implanting DDD/R devices in chronologically older, yet physiologically younger, patients is justifiable and good medical practice. Where right ventricular (RV) pacing is necessary and unavoidable, physicians should consider routinely placing RV leads on the RV mid- or outflow tract septum because these location are as good, if not better, for patients than the current practice of RV apical lead placement. In patients with AV block and asymptomatic yet moderate to severely depressed left ventricular systolic function, primary cardiac resynchronization therapy (CRT) should be strongly considered. Compelling clinical trial evidence does not yet exist to indicate that CRT should be the standard of care in patients with AV block and intact left ventricular systolic function. Right ventricular septal lead placement remains a reasonable option.