Question Stem

A 72-year-old woman with a history of hypertension, type 2 diabetes mellitus, and a recent myocardial infarction is seen in your clinic. Two months previously, she was hospitalized with a myocardial infarction and underwent successful revascularization of the left anterior descending artery with a drug-eluting stent. Following her myocardial infarction, an echocardiogram revealed an ejection fraction of 17%, and she was discharged on metoprolol succinate, lisinopril, spironolactone, and dapagliflozin with escalation to maximal tolerated doses over subsequent visits. A repeat echocardiogram performed today in your clinic reveals an ejection fraction of 26%. An electrocardiogram reveals normal sinus rhythm with a narrow QRS at a heart rate of 65 beats per minute. She is grateful for her cardiac rehabilitation program and reports no ongoing symptoms. Which of the following devices is indicated for placement at this time?

Answer choices

A

Implantable loop recorder

B

ICD

C

CRT-D

D

CRT-P

Explanation

The correct answer is B.

This patient suffered a myocardial infarction more than 40 days ago and has been on appropriate guideline-directed medical therapy since that time. Her left ventricular ejection fraction has improved but remains under 30%. For patients who have suffered a myocardial infarction over 40 days prior with LVEF ≤ 30% and NYHA Class I symptoms while receiving GDMT and have a reasonable expectation of meaningful survival for >1 year, an ICD is recommended for primary prevention of sudden cardiac death to reduce total mortality (Class I, LOE B-R).

The MADIT-II trial enrolled 1,232 patients with a prior myocardial infarction and LVEF ≤ 30% to prophylactic ICD or medical therapy. At a median follow-up of 20 months, the trial was terminated early for reduced all-cause mortality with prophylactic ICD. The DINAMIT trial later investigated the implantation of ICD in patients with MI and an LVEF of ≤ 35% at 6 to 40 days after the initial myocardial infarction. This trial found no differences in all-cause mortality between the two groups. Therefore, the current recommendation is to wait at least 40 days with GDMT prior to re-evaluation of left ventricular ejection fraction before proceeding with ICD implantation.

Cardiac resynchronization therapy entails implanted pacemakers to simultaneously pace both the RV and LV in order to improve electrical synchrony and generally provides benefit in those with systolic dysfunction and a wide left bundle branch block. Specifically, for patients who have LVEF ≤35%, sinus rhythm, left bundle branch block (LBBB) with a QRS duration ≥150 ms, and NYHA class II, III, or ambulatory IV symptoms on GDMT, CRT is indicated to reduce total mortality, reduce hospitalizations, and improve symptoms and QOL (Class I, LOE B-R). CRT implantation provides high economic value in this setting. CRT implantation carries a Class 2a recommendation for those with reduced LVEF (≤35%) and either a non-LBBB pattern with a QRS ≥150 ms or a LBBB with QRS duration 120-149ms. This patient with a narrow QRS does not have indications for CRT placement at this time.

Main Takeaway

ICD implantation is recommended as primary prophylaxis against ventricular arrhythmias for patients with LVEF ≤30% after 40 days following myocardial infarction despite use of GDMT.

Guideline Loc.

Section 6.1 and 7.4