TREADMILL (TMT) TEST IN BANGALORE​

TREADMILL (TMT) Test in BTM layout, Bangalore

Exercise testing is a noninvasive tool to evaluate the cardiovascular system’s response to exercise. Exercise is the body’s most common physiologic stress, and it places major demands on the cardiopulmonary system. Thus, exercise can be considered the most practical test of cardiac perfusion and function. Body increase its resting metabolic rate up to 20 times, cardiac output 6 times

Total body or ventilatory oxygen uptake (volume oxygen consumption [VO2]) is the amount of oxygen that is extracted from inspired air as the body performs work. The determinants of VO2 are cardiac output and the peripheral arteriovenous oxygen difference. Maximal arteriovenous difference is physiologically limited to roughly 15 to 17 mL/dL.  Thus maximal arteriovenous difference behaves more or less as a constant, making maximal oxygen uptake an indirect estimate of maximal cardiac output.

Myocardial oxygen uptake is the amount of oxygen consumed by the heart muscle. Myocardial oxygen demand is related to heart rate, blood pressure, left ventricular contractility (myocardial shortening per beat), and left ventricular wall stress(related to left ventricular pressure, wall thickness, and cavity size). It has been shown that myocardial oxygen uptake can be reasonably estimated by the product of heart rate and systolic blood pressure (double product). Higher the double product achieved the better is myocardial perfusion and prognosis

TREADMILL (TMT) Test

METABOLIC EQUIVALENTS : Exercise testing fundamentally involves the measurement of work. The MET, or metabolic equivalent, is a term commonly used clinically to express the oxygen requirement of the work rate during an exercise test on a treadmill or cycle ergometer. One MET is equated with the resting metabolic rate (approximately 3.5 mL of O2/kg/min),

EXERCISE PROTOCOLS : The exercise protocol should be progressive with even increments in speed and grade whenever possible. Smaller, even, and more frequent work increments are preferable to larger, uneven, and less frequent increases, because the former yield a more accurate estimation of exercise capacity In general, 6 to 12 minutes of continuous progressive exercise during which the myocardial oxygen demand is elevated to the patient’s maximal level is optimal for diagnostic and prognostic purposes. The protocol should include a suitable recovery or cool-down period.

TREADMILL PROTOCOL : Bruce protocol is popular, and a large diagnostic and prognostic data base has been published  The Bruce multistage maximal treadmill protocol has 3-minute periods to allow achievement of a steady state before workload is increased.

The exercise stress test is a useful screening tool for the detection of significant coronary artery disease. Documentation of the patient’s symptoms, medications, past and current significant illnesses, and usual level of physical activity helps the physician determine if an exercise stress test is appropriate. The physical examination must include consideration of the patient’s ability to walk and exercise, along with any signs of acute or serious disease that may affect the test results or the patient’s ability to perform the test. The test report contains comments about the maximal heart rate and level of exercise achieved, and symptoms, arrhythmias, electrocardiographic changes and vital signs during exercise. This report allows the clinician to determine if the test was “maximal” or “submaximal.” The quality of the test and its performance add to the validity of the results. The conclusion section of the test report indicates whether the test results were “positive,” “negative,” “equivocal” or “un-interpretable.” Further testing may be indicated to obtain optional information about coronary artery disease and ischemic risk if the test results were equivocal or un-interpretable.

TEST LIMITATIONS:

It is important to note that, while useful in detecting blockages, a cardiac stress test cannot tell how much an artery has hardened or thickened. The test is only a generalized measure of blood flow, which doctors can use to detect areas of restriction or diagnose the severity of CAD.

To pinpoint the location of the arterial obstruction, your cardiologist may need to perform a cardiac catheterization and coronary angiography test.

The cardiac stress test is also unable to predict how stable an arterial plaque may be or if and when a person may have a heart attack.

In terms of accuracy, a cardiac stress test is often open to interpretation, and results can vary based on the equipment used, the experience of the technician, and other factors that can change from day to day (such as whether a characteristic symptom occur during the test or not).

According to research from the American College of Cardiology, the sensitivity of a cardiac stress test without imaging is 68 percent, while its specificity is 77 percent. (Sensitivity refers to a test’s ability to render a correct positive diagnosis, while specificity refers to its ability to render a correct negative diagnosis).

Clinical experience, therefore, plays a huge role in how accurately a test result is rendered.

Contact Shree Vaishnavi Heart Centre for TREADMILL (TMT) Test in Bangalore.

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