Cardionerds: A Cardiology Podcast

Mr. S is an 80-year-old man with a history of hypertension, type II diabetes mellitus, and hypothyroidism who had an anterior myocardial infarction (MI) treated with a drug-eluting stent to the left anterior descending artery (LAD) 45 days ago. His course was complicated by a new LVEF reduction to 30%, and left bundle branch block (LBBB) with QRS duration of 152 ms in normal sinus rhythm. He reports he is feeling well and is able to enjoy gardening without symptoms, though he experiences dyspnea while walking to his bedroom on the second floor of his house. Repeat TTE shows persistent LVEF of 30% despite initiation of goal-directed medical therapy (GDMT). What is the best next step in his management?

A

Monitor for LVEF improvement for a total of 60 days prior to further intervention

B

Implantation of a dual-chamber ICD

C

Implantation of a CRT-D

D

Continue current management as device implantation is contraindicated given his advanced age

Explanation

Choice C is correct. Implantation of a CRT-D is the best next step.

In patients with nonischemic DCM or ischemic heart disease at least 40 days post-MI with LVEF ≤35% and NYHA class II or III symptoms on chronic GDMT, who have reasonable expectation of meaningful survival for >1 year,

ICD therapy is recommended for primary prevention of SCD to reduce total mortality (Class 1, LOE A). A transvenous ICD provides high economic value in this setting, particularly when a patient’s risk of death from ventricular arrhythmia is deemed high and the risk of nonarrhythmic death is deemed low.

In addition, 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, cardiac resynchronization therapy (CRT) is indicated to reduce total mortality, reduce hospitalizations, and improve symptoms and QOL. Cardiac resynchronization provides high economic value in this setting.

Mr. S therefore meets criteria for both ICD and CRT.

Choice A is incorrect. All patients should be on maximally tolerated doses of GDMT prior to consideration of device implantation to allow for assessment of LVEF recovery. Patients who have experienced myocardial infarction should be reassessed 40 days after the event and after achieving maximally tolerated doses of GDMT.

Choice B in incorrect. For patients in sinus rhythm with a LBBB morphology and QRS duration >150 ms with an LVEF ≤35%, there were significant improvements in 6-minute walk test performance, quality of life, NYHA classification, and LVEF after implantation of CRT. Mortality and hospitalizations were also found to be decreased in patients with CRT-P & CRT-D. Overall, CRT has been shown to have high economic value in these patients.

It should be noted that CRT has the most benefit in patients with a wide QRS (>150 ms), LBBB morphology, and LVEF ≤35%, though trials have shown a modest benefit in special populations. CRT has a Class 2a recommendation (LOE B-NR) in patients with LVEF ≤35%, sinus rhythm, and NYHA Class II, III, or ambulatory IV symptoms on GDMT, with either:

a) Non-LBBB pattern with a QRS duration ≥150 ms

b) LBBB with a QRS duration of 120 to 149 ms

Choice D is incorrect. If LVEF remains ≤35% in a patient with a life expectancy >1 year, trials have shown that ICD placement for primary prevention reduces sudden cardiac death and also has a high economic value. There is no indication that this patient has a life expectancy < 1 year.

Main Takeaway

In patients 40 days post-MI on GDMT with an LVEF that remains ≤35%, ICD therapy for primary prevention is appropriate and cost effective. For those additional with a LBBB and QRS >150 ms, CRT-D is also appropriate and cost effective.

Guideline Loc.

Section 7.4