A 53-year-old man comes to the office due to exertional dyspnea. He can walk only 2 blocks before becoming short of breath. The patient has no chest pain, palpitations, or syncope. He was hospitalized 8 months ago with heart failure with reduced ejection fraction and treated with diuretics. Cardiac catheterization showed nonobstructive coronary artery disease. Echocardiogram revealed left ventricle enlargement with an ejection fraction of 25%. Current medications include carvedilol, sacubitril-valsartan, furosemide, and spironolactone. Blood pressure is 112/68 mm Hg, pulse is 62/min, and oxygen saturation is 99% on room air. Jugular venous pressure is estimated at 7 cm H₂O. Breath sounds are decreased at the right lung base. The point of maximal impulse is displaced laterally. A regular heart rhythm and an S3 are heard. The liver span is 8 cm. The tip of the spleen is not palpated. There is mild edema of both ankles. Laboratory results are as follows: Repeat transthoracic echocardiogram is unchanged from the previous study. Which of the following ECG findings will change this patient's heart failure management?

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11ec193a_9750_6ae3_853d_1974170a55ae_MD0002_00 This patient with severe left ventricular dysfunction and New York Heart Association class III symptoms is on appropriate medical therapy, including a renin-angiotensin system blocker, beta blocker, and aldosterone antagonist. The next step is to determine eligibility for cardiac resynchronization therapy (CRT), which involves simultaneous pacing of both ventricles (biventricular pacing) or one ventricle in patients with bundle branch block. CRT is most effective in heart failure patients in sinus rhythm and with QRS duration ≥150 msec. CRT is also reasonable for patients with QRS duration >120 msec and <150 msec; the benefit of CRT in this group is clinically significant but less substantial. CRT improves left ventricular performance by restoring a more normal sequence of ventricular depolarization and contraction in patients with prolonged QRS duration. Biventricular pacing has been shown to improve exercise tolerance, reduce the need for hospitalization, and decrease overall mortality. Implantable cardioverter defibrillators are also beneficial in patients with severe left ventricular dysfunction by decreasing the risk of sudden death. (Choice A) Corrected QT interval (QTc) duration should be monitored closely in patients on antiarrhythmic therapy. Patients with prolonged QTc from any cause are at risk of torsade de pointes and sudden cardiac death. (Choice B) Precordial Q waves are generally seen in patients with prior myocardial infarction. However, ischemic cardiomyopathy is less likely in this patient with a recent cardiac catheterization showing nonsignificant coronary artery disease. (Choices D and E) A shortened PR interval may be seen in ventricular preexcitation syndromes (eg, Wolff-Parkinson-White) but is not a significant predictor of response to CRT. Similarly, QRS axis shift is not a good predictor of response to CRT. Educational objective: Cardiac resynchronization therapy (CRT) with a biventricular pacing device is recommended in patients with severe left ventricular systolic dysfunction (ejection fraction <35%), New York Heart Association class III or IV heart failure symptoms, and intraventricular conduction delay with QRS duration >150 msec. CRT is optional with QRS >120 msec but <150 msec. No clinical benefit with CRT has been noted in patients with systolic dysfunction and normal QRS duration (<120 msec). __________ References: Cardiac resynchronization therapy and QRS duration: systematic review, meta-analysis, and meta-regression. (http://www.ncbi.nlm.nih.gov/pubmed/25552880)

A 53-Year-Old Man Comes to the Office Due to Exertional