A rare sign of ischemia during exercise ECG: PR interval lengthening in the recovery period

Exercise electrocardiography (ECG) is one of the most commonly utilized tests in cardiology. Despite the drawbacks, exercise ECG is widely preferred due to low cost, standardization, and strong prognostic information. A prolonged PR interval during recovery has recently been proposed as an indicator of mortality. Herein, we report an interesting case of a patient who presented with the complaint of exertional dyspnea and exhibited PR lengthening during the recovery period on the exercise ECG. The patient had a PR interval of 240 ms before exercise, which decreased to 160 ms at peak stress. However, during recovery, the PR interval prolonged gradually, reaching 320 ms at the second minute and persisting at that length until the end of the recovery period. The patient achieved 87% of the age predicted maximum heart rate, and experienced non-disabling shortness of breath and a pressure sensation in the chest, with no apparent ST segment depression. Recovery parameters, including heart rate recovery and systolic blood pressure recovery, were also within normal limits. The patient underwent coronary angiography with the suspicion of CAD which revealed severe multi-vessel disease. This rare case emphasizes the importance of PR lengthening in the recovery period as a sign of severe ischemia, in addition to other signs, such as prominent ST-segment changes, chronotropic incompetence, impaired hemodynamic response, and poor exercise capacity during stress ECG evaluation.