Cardiac Resynchronization Therapy Using a Dual Chamber Pacemaker in Patients with Severe Left Ventricular Dysfunction and a Left Bundle Branch Block
A 51-year-old female with mild dyspnea of New York Heart Association (NYHA) functional class II heart failure and dysarthria due to a transient ischemic attack was diagnosed with dilated cardiomyopathy (ejection fraction 23%) through echocardiography and three-vessel disease through coronary angiography (proximal left anterior descending artery 60% stenosis, middle left anterior descending artery 60% to 70% stenosis, and distal left circumflex artery complete occlusion). The patient was transferred to our hospital for coronary artery bypass graft (CABG) surgery.\nShe had a diagnosis of hypertension and a history of an intraventricular block eight years earlier that was treated with digoxin, diuretics, beta-blockers, and an angiotensin-receptor blocker. Cardiomegaly was found on a posteroanterior chest radiograph, and a left bundle branch block (LBBB) pattern and prolonged QRS interval were identified on an electrocardiogram (ECG). Echocardiography also demonstrated left ventricle (LV) distension, severe LV dysfunction with a left ventricular ejection fraction (LVEF) of 28%, and mild mitral regurgitation. Pro-B-type natriuretic peptide was 2,070 pg/mL, and cardiac markers were normal. On-pump CABG was performed on day two of hospitalization. The left anterior descending coronary artery and diagonal branch were connected to the left internal mammary artery in situ, and a saphenous vein graft was used to connect the posterior descending artery and posterolateral artery. The patient had LV incompetence. Cardiac resynchronization therapy was attempted. Two temporary, unipolar, atrial pacing wires were inserted in the right atrium wall, and two temporary, bipolar, ventricular pacing wires were inserted into the right ventricular anterior wall and the left ventricular inferior wall. Temporary pacemakers (Medtronic 5388 Dual Chamber Temporary Pacemaker; Medtronic Inc., Minneapolis, MN, USA) were used since cardiac resynchronization therapy equipment was unavailable (). The rate was set to 66 ppm, and the sensitivities were set to 0.4 mV for the atria and 2.0 mV for the ventricles. The output was set to 10 mA for the atria and 20 mA for the ventricles. Wires inserted in the right atrium and left ventricular inferior wall were used, and a 196-millisecond PR interval verified from a preoperative ECG was used as a standard. QRS intervals were observed via ECG, and the PR interval was manipulated. The narrowest QRS was found using the PR interval standard, and the setting was changed (). Before cardiac resynchronization therapy (CRT) was initiated, intraoperative transesophageal echocardiography showed that the LVEF measured below 25%. On initiation of CRT, the LVEF increased visibly to about 40%. The cardiac output was measured immediately, and one hour and twelve hours after arrival in the intensive care unit. The cardiac output changed from 2.8, 2.4, and 3.6 L/min without pacing to 3.5, 3.4, and 3.5 L/min on initiation of pacing ().\nThe patient's postoperative vital status was stable on intravenous dopamine and nitroglycerin. CRT was used for 18 hours. A cardiac output of 3.8 L/min was maintained after turning the CRT off, and the cardiac output was 3.9 L/min when the patient was transferred to the general ward.