A 58-year-old man from rural Maharashtra presents to the emergency department with acute onset chest pain radiating to the left arm for 2 hours. He is diaphoretic and anxious. Vital signs: BP 110/70 mmHg, HR 98/min, RR 20/min. ECG shows ST elevation in leads II, III, and aVF. Troponin I is elevated at 2.5 ng/mL. The nearest PCI-capable centre is 180 km away with an estimated door-to-balloon time of 4 hours. The patient has no contraindications to thrombolysis. Which thrombolytic agent is most appropriate for this patient, and why?

Explanation

## Clinical Context This patient has acute STEMI (ST-elevation myocardial infarction) with inferior wall involvement and is presenting within the therapeutic window (2 hours). Primary PCI is not feasible within the recommended 120-minute door-to-balloon time, making thrombolysis the appropriate reperfusion strategy. ## Thrombolytic Agent Selection **Key Point:** In resource-limited settings and when PCI is not available within 120 minutes, streptokinase remains the first-line thrombolytic agent in India due to cost-effectiveness and proven efficacy in STEMI. ### Comparison of Thrombolytics | Agent | Fibrin Selectivity | Cost | Door-to-Needle Time | Reperfusion Rate | Key Limitation | |-------|-------------------|------|-------------------|------------------|----------------| | Streptokinase | Low | Very low (₹2,000–3,000) | 30–60 min | 50–60% | Antigenic; hypotension; re-administration risk | | Alteplase | High | High (₹15,000–20,000) | 30–90 min | 70–80% | Cost; weight-based dosing complexity | | Reteplase | High | High (₹18,000–25,000) | 30 min | 65–75% | Cost; bolus-based (less titratable) | | Urokinase | Intermediate | High (₹12,000–18,000) | 30–60 min | 55–65% | Cost; limited availability in India | **High-Yield:** Streptokinase is the WHO-recommended and Indian guideline-preferred agent for STEMI in resource-limited settings. It achieves TIMI 3 flow in ~50–60% of cases and is cost-effective for mass deployment. ## Dosing & Administration 1. **Streptokinase 1.5 million units** diluted in 100 mL normal saline, infused IV over 60 minutes. 2. Administer **aspirin 300 mg** (chewed) + **clopidogrel 600 mg** loading dose concurrently. 3. Monitor for: - Hypotension (most common; manage with IV fluids, leg elevation) - Allergic reactions (rash, fever, anaphylaxis — rare but serious) - Reperfusion arrhythmias (accelerated idioventricular rhythm, bradycardia) **Clinical Pearl:** Streptokinase is antigenic and should NOT be re-administered within 5 years of prior exposure due to neutralizing antibodies. Always obtain a detailed history of prior streptococcal infection or previous SK use. ## Rationale for Streptokinase in This Case - **Cost:** ₹2,000–3,000 vs. ₹15,000–25,000 for fibrin-selective agents — critical in rural India. - **Availability:** Universally stocked in primary health centres and district hospitals. - **Guideline alignment:** Indian Society of Cardiology (ISC) and ACC/AHA guidelines recommend SK as first-line when PCI unavailable. - **Efficacy:** Mortality reduction comparable to alteplase in the GUSTO-I and INJECT trials (30-day mortality ~7% with SK). **Warning:** Do NOT delay thrombolysis while awaiting transfer for PCI. "Time is myocardium" — every 30-minute delay increases 1-year mortality by ~7.5%. ## Post-Thrombolysis Management 1. Assess for reperfusion signs (ST resolution >50%, pain relief, reperfusion arrhythmias) at 60–90 minutes. 2. If no reperfusion → **rescue PCI** is indicated. 3. Continue dual antiplatelet therapy (aspirin + clopidogrel) for 12 months. 4. Beta-blocker, ACE inhibitor, and statin initiation as per post-MI protocols. **Mnemonic: STEMI Thrombolysis Checklist — "ABCDE"** - **A**spirin + Anticoagulation (heparin or enoxaparin) - **B**eta-blocker (if no contraindication) - **C**hoose thrombolytic (SK in resource-limited; alteplase if fibrin-selective preferred) - **D**oor-to-needle <30 minutes - **E**valuate reperfusion at 60–90 minutes; rescue PCI if failed