Failure of Ventricular Capture and Pacemaker Exit Block Secondary to Moderate Hyperkalemia

Hyperkalemia is a life threatening metabolic condition. When the K level increases, the intraventricular conduction velocity is decreased and the paced QRS complex widens. When the K level reaches 7 mEq/L pacing thresholds could increase, with or without increased latency. Occasionally failure to capture appears at a lower level, especially in the presence of heart disease. We report a case where moderate hyperkalemia caused pacemaker exit block and a failure of ventricular pacemaker capture. An 81-year-old woman was admitted to our institution with bradycardia, weaknessand presyncope. She had a history of type 2 diabetes mellitus and chronic kidney disease (eGFR of 12 ml/min). Patient underwent bivalvular mechanic mitral- aortic valve replacement 13 years ago. 

Six months after cardiac surgery the patient underwent a VVI pacemaker implant (Vitatron G20) for permanent atrial fibrillation with slow ventricular response. The patient’s pacemaker was programmed VVI with a lower rate limit 70 beats/min. In the last weeks, congestive heart failure symptoms had appeared, thus loop diuretic dose was increased (Furosemide 100 mg per day). Her medications also included digoxin 0.25 mg per day, warfarin 2 mg per day, and insulin; thus she didn’t take antiarrhythmic drugs at admission physical examination revealed a pulse rate of 42 per minute, blood pressure of 95/50 mmHg, and an oxygen saturation of 93% on room air with a respiratory rate of 24. Signs and symptoms of acute heart failure were present.Read more............