Should heparin be started in a patient with ST depressions on inferior and lateral leads, chest pain, tachycardia, and negative troponins and BNP (brain natriuretic peptide), who has already received aspirin?

Should Heparin Be Started in This Patient?

Yes, heparin should have been started immediately in this patient presenting with ST depressions on inferior and lateral leads, chest pain, and tachycardia, even with negative troponins. This patient meets criteria for acute coronary syndrome (ACS) without ST-segment elevation, and current guidelines recommend anticoagulation with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) in addition to aspirin 1.

Rationale for Heparin Initiation

The presence of ST-segment depression on ECG is a high-risk feature that mandates anticoagulation regardless of initial troponin results. The European Society of Cardiology guidelines explicitly state that patients with ST-segment changes without persistent ST-elevation require initial medical treatment including aspirin AND either LMWH or unfractionated heparin 1. The ACC/AHA guidelines similarly recommend that antiplatelet therapy (aspirin) should be combined with heparin for patients with non-ST-elevation ACS 1.

Why Negative Troponins Don't Change Management

• Serial troponin measurements over 6-12 hours are required to exclude myocardial infarction, and a single negative troponin does not rule out ACS 1, 2.
• Treatment decisions should be based on ECG findings and clinical presentation, not delayed pending troponin results 3, 2.
• The American Heart Association specifically advises against withholding aspirin (and by extension, appropriate anticoagulation) while waiting for troponin results in patients with chest pain 3.

Specific Heparin Dosing Recommendations

For unfractionated heparin in non-ST-elevation ACS:

• Initial bolus: 60-70 units/kg (maximum 5,000 units) 1, 4
• Continuous infusion: 12-15 units/kg/hour 1, 4
• Target aPTT: 50-70 seconds (or 1.5-2.0 times control) 1, 5

Alternatively, LMWH (enoxaparin) can be used:

• Evidence suggests LMWH may be superior to UFH in some trials, with more predictable anticoagulant effects and no need for monitoring 1.
• Two major trials (ESSENCE and TIMI-11B) showed enoxaparin was at least as effective as UFH, with trends toward better outcomes 1.

High-Risk Features Present in This Patient

This patient demonstrates multiple high-risk features that strengthen the indication for immediate anticoagulation:

• ST-segment depression on inferior and lateral leads - This represents significant ischemic ECG changes and places the patient in the high-risk category 1.
• Tachycardia at 130 bpm - This may indicate hemodynamic stress or ongoing ischemia 1.
• Active chest pain - Symptomatic presentation with ECG changes defines unstable angina at minimum 1.

The European Society of Cardiology specifically identifies patients with ST-segment depression as high-risk who require early angiography and intensive antithrombotic therapy including heparin 1.

Evidence Supporting Combined Aspirin and Heparin

While aspirin alone reduces MI risk, the addition of heparin provides additional benefit, particularly for preventing refractory angina:

• A meta-analysis of six trials showed that aspirin plus heparin reduced death or MI from 10.3% to 7.9% compared to aspirin alone, though this did not reach statistical significance (OR 0.74,95% CI 0.5-1.09, p=0.10) 1.
• Heparin was particularly effective at reducing refractory angina (risk reduction from 22.9% to 8.5%, p=0.002) 1, 6.
• In the landmark Theroux trial, heparin reduced MI incidence to 0.8% compared to 11.9% with placebo (p<0.0001) 1, 6.

Critical Pitfalls to Avoid

Common errors in managing this clinical scenario:

• Delaying anticoagulation until troponins return positive - This represents undertreatment of a high-risk ACS patient 3, 2.
• Relying on a single ECG or troponin - Serial measurements are mandatory, and dynamic ECG changes may evolve 1, 3.
• Assuming symptom resolution means low risk - The hyperdynamic LV on bedside ultrasound may indicate catecholamine surge or compensatory response to ischemia, not reassurance 2.
• Failing to address the tachycardia - Rate control with beta-blockers should be considered once hemodynamically stable 1.

Additional Management Considerations

Beyond heparin, this patient requires:

• Continuous cardiac monitoring with immediate availability of resuscitation equipment 2.
• Repeat ECG within 10 minutes if symptoms recur, and serial ECGs at 15-30 minute intervals during the first hour 3, 2.
• Second troponin measurement at 6-12 hours from symptom onset 1, 2.
• Beta-blocker therapy if not contraindicated (heart rate >50, systolic BP >100 mmHg, no heart failure) 1.
• Consideration of clopidogrel (300-600 mg loading dose) given the high-risk ECG features 1, 2.
• Cardiology consultation for risk stratification and potential early invasive strategy 1.

The Hyperdynamic LV Finding

The hyperdynamic left ventricle on bedside ultrasound does not exclude ACS and should not influence the decision to anticoagulate:

• This finding may represent a catecholamine-driven compensatory response to ischemia or tachycardia 2.
• Regional wall motion abnormalities may not be apparent if ischemia is intermittent or if the examination was performed between episodes 1.
• Normal or hyperdynamic LV function does not rule out significant coronary disease or ongoing ACS 1.