Treadmill Testing- “Episodic Ischemia” in a middle aged woman aged 46 years

The treadmill ECG stress test is commonly used as a screening test to identify myocardial ischaemia. During exercise, the physiological increase in heart rate is due to a decrease in vagal tone followed by an increase in sympathetic tone and the sufficient effort during treadmill ECG stress testing is defined as achieving 85% of the age-predicted maximal heart rate. The increase in sympathetic tone and vasodilation during exercise generally causes a rise in blood pressure. An exaggerated blood pressure response, defined as a peak systolic blood pressure of > 210 mmHg in men and > 190 mmHg in women was shown to predict the risk of hypertension in normotensive individuals, A drop in systolic blood pressure > 10 mmHg is an indication to terminate the treadmill ECG stress tests, as it could be due to myocardial ischaemia leading to left ventricular dysfunction. In addition to the evaluation of CAD, the treadmill ECG stress test is also often used to evaluate for chronotropic incompetency, in which the patient is unable to mount an adequate heart rate response to exercise, leading to symptoms such as effort-related dyspnoea and lethargy.The Bruce protocol is the most commonly used and it consists of a total of seven stages, with a gradual increment in the speed and gradient of the treadmill. Each stage lasts three minutes to allow the patient to acclimatise to the specific speed and gradient before advancing to the next stage. The MET value increases as the patient advances to higher stages of the Bruce protocol. Exercise intensity during the treadmill ECG stress test is calculated in METs, which reflect the amount of oxygen consumed per minute. 1 MET is equal to 3.5 mL/min/kg of oxygen used. Continuous ECG monitoring is carried out throughout the test and into the recovery period to assess for any changes in the ST segments due to limitation of coronary blood flow may lead to myocardial ischaemia, as well as for arrhythmia. The test is often stopped before completing Stage 7, when the patient achieves the target heart rate or is symptomatic, or when the test is positive.The duration of ST-segment depression is also important, as prolonged recovery after peak stress is consistent with a positive treadmill ECG stress test. Another finding that is highly indicative of significant CAD is the occurrence of ST-segment elevation > 1 mm (often suggesting transmural ischemia) and these patients are frequently referred urgently for coronary angiography. A 46-year-old female developed anginal episodes during treadmill testing and further evaluation revealed a congenutal coronary anomaly.