What's the next step for a patient with a history of Non-ST-Elevation Myocardial Infarction (NSTEMI) and stent placement who presents with dizziness, diaphoresis, and bradycardia?

Immediate Management of Symptomatic Bradycardia in a Post-NSTEMI Patient with Stents

This patient requires immediate cardiac monitoring, 12-lead ECG, and urgent cardiology consultation to evaluate for acute coronary occlusion, high-grade AV block, or medication-induced bradycardia—any of which could be life-threatening in this clinical context. 1

Immediate Assessment and Monitoring

Obtain a 12-lead ECG within 10 minutes of presentation to evaluate for:

• Acute ST-segment changes indicating recurrent ischemia or stent thrombosis 1
• High-grade AV block (second-degree type II or third-degree) 1
• New conduction abnormalities 1

Place the patient on continuous cardiac monitoring immediately with emergency resuscitation equipment and defibrillator at bedside, as life-threatening arrhythmias occur in 2.6-5.7% of acute MI patients, with 80% occurring within the first 12 hours. 1

Critical Differential Diagnosis

The combination of dizziness, diaphoresis, and bradycardia (HR 35-60) in a patient with prior NSTEMI and stents raises three urgent possibilities:

1. Acute Coronary Occlusion (Stent Thrombosis or New Event)

• Bradycardia with diaphoresis suggests vagal response to inferior/posterior ischemia 1
• STEMI(-) OMI patients experience significant delays to catheterization but have outcomes similar to STEMI(+) OMI 2
• Immediate invasive strategy (<2 hours) is mandated if there is hemodynamic instability, ongoing chest pain refractory to medical treatment, or life-threatening arrhythmias 1

2. High-Grade AV Block

• Second-degree type II or third-degree heart block are absolute contraindications to beta-blocker administration 1, 3
• PR interval >0.24 seconds contraindicates beta-blocker use 1, 3

3. Medication-Induced Bradycardia

• Beta-blockers should not be administered to patients with severe bradycardia (<50 bpm) 1
• Review current medications for rate-controlling agents 3

Immediate Interventions

Obtain cardiac biomarkers (high-sensitivity troponin) immediately:

• Rise or fall in troponin compatible with MI mandates early invasive strategy within 24 hours 1
• Peak troponin T >1.0 ng/mL with acute culprit lesion defines occlusion MI regardless of ECG findings 2

Assess hemodynamic stability:

• If systolic BP <90 mmHg or signs of cardiogenic shock: immediate invasive strategy (<2 hours) and consider intra-aortic balloon pump 1
• Nitrates are contraindicated with severe bradycardia (<50 bpm) or systolic BP <90 mmHg 1

Hold beta-blockers immediately if:

• Heart rate <50 bpm 1
• Signs of heart failure or low-output state 1, 3
• PR interval >0.24 seconds or any degree of heart block 1, 3

Risk Stratification and Timing of Angiography

Calculate GRACE score to determine urgency of catheterization:

• GRACE score >140 mandates early invasive strategy within 24 hours 1
• Hemodynamic instability, ongoing ischemia, or life-threatening arrhythmias require immediate catheterization (<2 hours) 1

Arrhythmia monitoring should continue uninterrupted for ≥12-24 hours, with reassessment every 24 hours until the patient has been event-free for 12-24 hours. 1

Antiplatelet and Anticoagulation Management

If acute coronary syndrome is confirmed:

• Aspirin 162-325 mg immediately if not already on maintenance therapy 4
• Continue existing P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) 4, 5
• Administer parenteral anticoagulation (unfractionated heparin, enoxaparin, fondaparinux, or bivalirudin) 4

Do not discontinue antiplatelet therapy unless there is active bleeding, as this increases risk of stent thrombosis. 5

Critical Pitfalls to Avoid

• Do not delay catheterization in STEMI(-) patients with suspected occlusion MI—they have median time to catheterization of 437 minutes versus 41 minutes for STEMI(+) patients, despite similar adverse outcomes 2
• Do not administer IV beta-blockers to patients with bradycardia, heart failure signs, or increased shock risk—this may be harmful 1, 3
• Do not assume stable vital signs exclude acute coronary occlusion—NSTEMI patients can have acute occlusion without ST elevation 2
• Do not discharge without 12-24 hours of continuous monitoring after any intervention, as 90-92% of ventricular arrhythmias occur within 48 hours of PCI 1