Prevention of Effective Cardiac Resynchronization Therapy by Frequent Premature Ventricular Contractions in a Patient with Nonischemic Cardiomyopathy

History

In 2002 the patient was diagnosed with Global Initiative for Chronic Obstructive Lung Disease stage II chronic obstructive pulmonary disease and in 2004 with first-degree atrioventricular block. In June 2011 he was admitted for decompensated heart failure. Echocardiography revealed a mildly dilated left ventricle, left ventricular ejection fraction (LVEF) of 20%, and grade III mitral regurgitation. Coronary angiography showed no significant coronary artery disease. Frequent premature ventricular contractions were observed during admission. Medical therapy for heart failure was initiated, and the patient was scheduled for reevaluation.

In October 2011 frequent premature ventricular contractions were reported on a 24-hour Holter monitor (28% of all QRS complexes, with one dominant morphology accounting for 99% of all premature ventricular contractions). Drug therapy with metoprolol 75 mg twice daily was not effective, sotalol was not tolerated, and metoprolol was continued.

In December 2011 the patient was readmitted for intermittent total atrioventricular block reported on a 24-hour Holter monitor. He was in New York Heart Association (NYHA) class III. On an echocardiogram, LVEF was 30%, with grade I to II mitral regurgitation. Despite discontinuation of metoprolol therapy, the total atrioventricular block became permanent. A temporary pacemaker was inserted, followed by cardiac resynchronization therapy defibrillator (CRT-D) implantation.

Current Medications

The patient was taking calcium carbasalate (Ascal) 100 mg daily, spironolactone 12.5 mg daily, simvastatin 40 mg daily, perindopril 4 mg daily, furosemide 40 mg daily, and metoprolol 50 mg twice daily.

Current Symptoms

The patient had marked limitation of physical activity (NYHA class III), with no chest pain or collapse.

Physical Examination

• BP/HR: 125/55 mm Hg/60 bpm

• Height/weight: 168 cm/72 kg

• Neck veins: Not distended

• Lungs/chest: Unremarkable

• Heart: Holosystolic murmur, grade 2/6, loudest at the apex

• Abdomen: Unremarkable

• Extremities: No peripheral edema

Laboratory Data

• Hemoglobin: 8.8 mmol/L

• Hematocrit/packed cell volume: 41.9%

• Mean corpuscular volume: 96 fL

• Platelet count: NA

• Sodium: 138 mmol/L

• Potassium: 4.7 mmol/L

• Creatinine: 81 µmol/L

• Blood urea nitrogen: 7.5 mmol/L

Electrocardiogram

Findings

An electrocardiogram revealed biventricular pacing with frequent premature ventricular contractions and QRS during biventricular pacing at 160 ms ( Figure 27-1 ). Premature ventricular contractions occurred with slightly varying morphology, all right bundle branch block (RBBB) type of morphology (defined as dominant R in precordial lead V ₁ ), left superior axis, transition V _4-5 .

Echocardiogram