Syncope During Treadmill Test
A 58-year-old man with a history of hypertension and smoking is undergoing a treadmill exercise stress test. At 6 minutes into the Bruce protocol (stage 3, 9 METs), his heart rate is 140 bpm, blood pressure is 150/90 mmHg, and he reports mild fatigue. Suddenly, he develops lightheadedness, and the ECG shows a 3-second pause followed by a junctional escape rhythm at 40 bpm. He becomes pale and diaphoretic. The technician must decide whether to stop the test and what immediate actions to take.
1. What is the most appropriate immediate action for the technician?
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The technician should immediately stop the treadmill, call for emergency assistance, and help the patient to a supine position with legs elevated. The patient is experiencing syncope with a significant bradyarrhythmia (pause and junctional escape), which is a relative contraindication to continuing the test. The priority is patient safety: stopping exercise reduces vagal tone and myocardial oxygen demand, and supine positioning improves cerebral perfusion. The technician should also administer oxygen if available and monitor vital signs continuously until emergency personnel arrive. Documentation of the event and ECG tracing is essential.
2. What are the possible causes of the bradyarrhythmia in this context, and how would you differentiate them?
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Possible causes include vasovagal syncope (excessive vagal tone from exercise), ischemia-induced conduction system disease, or a primary arrhythmia. Vasovagal syncope often presents with prodromal symptoms (nausea, warmth, diaphoresis) and bradycardia followed by hypotension; the rhythm typically resolves with supine positioning. Ischemic bradyarrhythmia may be accompanied by ST-segment changes or chest pain and may not resolve quickly. In this case, the absence of chest pain and the rapid onset after peak exercise suggest vasovagal, but ischemia cannot be excluded. The technician should note the timing, symptoms, and ECG changes, and the physician may order further evaluation such as coronary angiography if ischemia is suspected.