The acute effects of transvenous biventricular pacing in a patient with congestive heart failure

Cardiac resynchronization therapy and tools to identify responders

Heart failure is a major epidemic. Many people with heart failure struggle with refractory symptoms despite optimal medical therapy. Those with severe left ventricular dysfunction and ventricular conduction delay are at significant risk from either dying suddenly or dying from progression of their heart failure. Cardiac resynchronization therapy (CRT) improves hemodynamics and symptoms of heart failure and has recently been shown to improve survival. One problem facing the use of CRT is that 30% of patients fail to respond. The dominant theory is that QRS duration (electrical dyssynchrony) does not accurately reflect mechanical dyssynchrony. Echocardiographic tools have recently been developed that enable clinicians to assess the degree of mechanical dyssynchrony in patients being considered for CRT. These tools are able to predict with a significant amount of accuracy whether a patient will respond to CRT. This allows for a more refined approach to evaluating patients for CRT and optimizing the treatment of congestive heart failure.

Frequent ICD shocks due to double sensing in patients with bi-ventricular implantable cardioverter defibrillators

Biventricular pacing has emerged as a modality for treatment of patients with heart failure. Combined biventricular pacers and implantable cardioverter defibrillators offer treatment of heart failure as well as protection from sudden cardiac death. However, inappropriate ICD shocks as a result of double sensing due to widely spaced ventricular bipoles may pose a significant problem in these patients. We examined the ICD records of twenty-three patients with biventricular ICDs, and evaluated all episodes of double sensing that resulted in aborted or delivered therapy. In follow-up of 3.7 +/- 2.6 months, thirty-three shocks in fifteen episodes occurred in five patients (21.7%) due to double sensing. Four patients (17.4%) had aborted shocks due to double sensing. All episodes resulting in shock occurred because of sinus tachycardia or supraventricular tachycardia above the upper programmed pacing rate of the device with resultant AV conduction and double sensing of the nonpaced ventricular depolarization. In conclusion, double sensing of the R-wave is a common and clinically important cause of inappropriate ICD detection and shock in patients with biventricular ICDs. Appropriate programming of the ICD can prevent episodes of inappropriate shocks.

Cardiac arrhythmias: drugs and devices

This review focuses on the important role played by the various types of remedial therapy in the prevention and treatment of perioperative cardiac arrhythmias. It discusses the new concepts of arrhythmogenesis and pro-arrhythmia; the long QT interval syndrome; newer, more selective class 3 antiarrhythmic drugs; cardiac rhythm management devices; drugs or devices used as prophylaxis for postoperative atrial arrhythmias; intravenous amiodarone for destabilizing ventricular arrhythmias; and preoperative potassium imbalance.