Tetralogy of fallot and biventricular heart failure: Submitted by Adam J. Small, MD and Jeremy Moore, MD

1. Electrical causes of cardiac dysfunction include absence of AV synchrony, dyssynchronous ventricular activation, and tachycardia-induced cardiomyopathy. 2. Each of these three factors should be considered in any patient with severe ventricular dysfunction and every effort undertaken to eliminate them. Elimination or reduction of tachyarrhythmia burden (using drugs, ablation, surgery, and or antitachycardia pacing), reducing dyssynchrony (by elimination of ventricular pacing or appropriate resynchronization therapy), and providing AV synchrony by placement of appropriate leads are all important in the management. 3. Transplant can be delayed, or even avoided, by the abovementioned measures in select patients. Final diagnosis: Pacing-induced cardiomyopathy Interventions: Tachyarrhythmias were controlled with a combination of amiodarone and flecainide. The patient was taken to the electrophysiology laboratory for electroanatomical mapping of the right atrium. The baseline rhythm was noted to be junctional at a rate of 60 beats/minute. The intrinsic QRS duration was 176 ms. High-density voltage mapping of the right atrium demonstrated diffuse scarring, but with a small region of viable myocardium, with p wave of 0.8-1.3 mV and acceptable pacing threshold (Figure 2). The implantable cardioverter-defibrillator generator was removed and the electroanatomical map was used to guide a new pacing lead (St Jude Tendril STS, 46 cm; St Jude Medical, St Paul, MN, USA) to this location. The following hemodynamics were recorded during the procedure: Condition #1 (atrial pacing 90 beats/minute) Cardiac output 3.10 liters/minute, cardiac index 1.78 liters/minute/m2ÐA pressure: 40/24/30 mm Hg, wedge pressure: 24 mm Hg Condition #2 (junctional rhythm) Cardiac output 2.65 liters/minute, cardiac index 1.64 liters/minute/m2ÐA pressure: 53/20/30 mm Hg, wedge pressure: 23 mm Hg Outcome: The patient improved with AAI pacing. He was discharged from the hospital with milrinone. Within 3 months, his ventricular function demonstrated improvement by echocardiography. Within 6 months, he was weaned off milrinone.