A 72-year-old woman with past medical history significant for hypertension, hyperlipidemia, and rheumatoid arthritis is brought to the emergency department by EMS for chest pain and found to have an anterior STEMI. Coronary angiography reveals 100% occlusion of her proximal LAD. During revascularization, she develops complete heart block, so a temporary transvenous pacing wire is inserted. After the PCI, she is monitored in the CCU. Three days later, she continues to have an intermittent high-grade AV block along with shortness of breath. Transthoracic echocardiogram demonstrates mildly reduced LV function with anterior and anteroseptal hypokinesis. What is the best next step?

A

Continue to monitor with temporary transvenous pacer

B

Permanent pacemaker implantation

C

Start dopamine infusion

D

Administer atropine as needed

Explanation 

The correct answer is B – permanent pacemaker implantation.

Patients with STEMI with second- or third-degree atrioventricular blocks have higher in-hospital mortality than those without high-degree atrioventricular blocks. Patients who present with ACS with complete heart block have a higher incidence of cardiogenic shock, ventricular arrhythmia, and death. In a contemporary cohort of patients with AMI, the incidence of high-degree atrioventricular block has decreased from 4.2% to 2.1%; however, increased morbidity and mortality remain despite reperfusion therapy in those with high-degree atrioventricular block. A pooled analysis of 30,000 patients found that high-degree atrioventricular block, asystole, and electromechanical dissociation are infrequent complications of NSTEMI but are associated with increased short-term mortality. High-degree atrioventricular block is not considered to be responsible for the increased mortality but is a surrogate marker of larger infarct size. Temporary pacemaker insertion in the setting of ACS in patients with high-degree atrioventricular blocks and other pacer indications has been found to improve post-discharge survival. Permanent pacemaker insertion is recommended with unresolved high-degree atrioventricular block that persists >72 hours.

The 2025 ACS guidelines give a Class 1 recommendation (LOE B-NR) for permanent pacing in patients presenting with an AMI with sustained evidence of second-degree Mobitz type II atrioventricular block, high-grade atrioventricular block, alternating bundle-branch block, or third-degree atrioventricular block (persistent or

infranodal).

This patient has had more than 72 hours of ongoing high-grade heart block post-MI. Continuous use of temporary transvenous pacing (answer choice A), dopamine infusion (answer choice C), or atropine (answer choice D) will not permanently treat the bradyarrhythmia and hence none of these answers represents the next best treatment option for the patient.

Main Takeaway

In patients presenting with an AMI with sustained (i.e. >72 hours) evidence of second-degree Mobitz type II atrioventricular block, high-grade atrioventricular block, alternating bundle branch block or third-degree atrioventricular block (persistent or infra-nodal), permanent pacing is indicated.

Guideline Loc.

Section 9.2