A decrease in parasympathetic activity and an increase in sympathetic activity lead to a rise in HR immediately after aerobic exercise is started.¹⁰ There is a linear increase in HR with continued exercise. The most widely used equation for maximum predicted HR is 220 minus age in years for men and 80% of the above for women.¹¹,¹² Wide variability exists among subjects when the formula to predict maximum HR is used. Increase in HR rather than increase in stroke volume is responsible for a far greater augmentation in cardiac output during strenuous exercise. Stroke volume increases by about 50% with exercise, whereas the HR increase is more than 250%.¹³ Although a resting cardiac output is about 5.5 L/min, an increase of cardiac output up to 30 L/min can be seen in long-distance runners and other well-conditioned athletes. However, the behavior of HR response during exercise could be variable in patients. An exaggerated HR response to exercise is seen in deconditioning, anemia, or LV dysfunction, whereas an inadequate HR response to exercise (“chronotropic incompetence”) is seen with sinus node dysfunction. Multiple determinants, such as blood volume, peripheral vascular resistance, medications (beta-blockers), and body position, can also affect HR response to exercise.

HR response after termination of exercise can offer prognostic clues in heart disease. A delayed HR recovery, that is, a slow return of HR back to normal after exercise is terminated, suggests decreased vagal activity, an important predictor of mortality in patients with and without angiographic coronary artery disease.¹⁴,¹⁵,¹⁶ Despite some variability, most studies define an abnormal HR recovery as the inability to drop the HR by 12 to 21 bpm, 1 minute after the termination of exercise.¹⁷,¹⁸,¹⁹

On average, the systolic BP rises by 10 mm Hg/MET during exercise, whereas the diastolic pressure remains unchanged or decreases slightly.⁵ Return of BP to the baseline preexercise level within about 6 minutes after termination of exercise is expected in healthy individuals.²⁰

In preparation for the exercise ECG test, it is important to perform a thorough clinical assessment of the patient with emphasis on the presence of an appropriate indication and absence of any contraindications. Evaluation of preexisting symptoms particularly those attributable to relevant comorbidities is warranted.

A brief history focused on risk factors and symptoms leading to stress testing should be obtained from the patient and supplemented by chart review. Symptom review allows for identification of symptoms to monitor during the test, especially in patients who present with atypical symptoms of ischemia. Evaluation of a patient’s functional capacity is important for the appropriate selection of exercise protocol, reducing the risk of physical injuries during exercise, and improving the overall safety of the test. Assessment of pretest probability of ischemic heart disease is essential for confirming the appropriateness of ECG exercise testing rather than another type of stress modality. The ideal candidate for ECG exercise testing has a predicted intermediate pretest probability (15%-65%) for ischemic heart disease test, based on the type of chest pain (typical angina, atypical angina, or noncardiac chest pain) and sex of the patient.¹ False-positive exercise ECG tests are frequent in those with lower pretest probability, and false-negative tests are of concern in those with higher than 65% pretest probability. Physical examination should be performed with particular attention to the presence of murmurs and orthopedic or neurologic conditions that limit physical activity. Precordial murmurs including late peaking aortic systolic murmurs
should warrant echocardiography to exclude severe aortic stenosis prior to the test. Exercise ECG test is of high value for the diagnosis of ischemia only when the resting ECG is normal.¹ In the presence of ST depression, LV hypertrophy, left bundle branch block (LBBB), pre-excitation, or continuously paced rhythm on the resting ECG, exercise ECG becomes uninterpretable for the presence of ischemia.