TMT is short for treadmill test. Treadmill is a device used for exercise testing. The subject walks on a motorized belt, the speed and gradient of which can be adjusted. There are various protocols for treadmill testing. One popular protocol is known as the Bruce protocol in which the initial slope (gradient) of the treadmill is 10 percent and the gradient increases in steps of 2 percent in each three minute stage. The initial speed is 1.7 miles per hour. It increases to 2.5 miles per hour in the second stage. So on it goes up to stage seven or as much as the subject can tolerate. Now a days the test is computerized so that the speed and gradient of the treadmill is controlled by a computer console which also monitors the ECG of the subject and displays it. The computerized console also measures the various ECG parameters and displays alerts if necessary. The blood pressure is measured and entered in the console by the operator. The test is conducted in the medical setting by a trained technician with resuscitatory equipment at hand in case of any untoward events.
Author Archives: Johnson Francis
What happens to blood pressure when the heart contracts?
When the heart contracts, blood is pushed into the blood vessels through the aorta from the left ventricle. This increases the pressure in the blood vessels. The pressure in the blood vessels when the heart contracts is known as the systolic blood pressure. The blood pressure in the vessels fall when the heart relaxes and the pressure in the blood vessels when the heart relaxes is known as the diastolic blood pressure. Systole is the technical term for contraction of the heart and diastole the term for relaxation of the heart.
Ballon mitral valvotomy – the modern treatment for mitral stenosis
Long back, mitral stenosis (narrowing of the valve between the left atrium and left ventricle) used to be treated by a surgery known as closed mitral valvotomy in which the surgeon used to open the chest and introduce a mechanical device to enlarge the narrowed valve through the tip of the left ventricle. Currently this procedure has become obsolete and almost extinct with the development of balloon mitral valvotomy. In this procedure, balloon at the tip a long tube (balloon catheter) is used to enlarge the narrowed valve. The balloon catheter for this procedure is introduced through the femoral vein in the groin under local anaesthesia. It moves up the inferior vena cava into the right atrium. Entry from right atrium to left atrium is preformed using a needle and dilated introduced through the femoral vein prior to introduction of the balloon tipped catheter. From the left atrium, the balloon is introduced into the left ventricle, across the narrowed mitral valve. Once it is positioned across the mitral valve, the balloon is inflated using dilute radiocontrast to achieve enlargement of the narrowed mitral valve. The whole procedure is guided by X-ray fluroscopy and is done in a cardiac catheterization laboratory, by trained personnel.
Dyeless angiography
Angiography or imaging of blood vessels usually require injection of a radiocontrast (dye) into the blood vessels and imaging them with X-ray technology. Dyeless angiography is possible with magnetic resonance imaging where the signals from the moving hydrogen particles in blood give the image. This is known as magnetic resonance angiography. This avoids the risk of radiocontrast dyes which could produce adverse effects like allergic reaction, kidney dysfunction, transient suppression of cardiac function producing fall in blood pressure etc.
Another form of angiography which does not use radiocontrast material is carbon dioxide angiography in which gaseous carbon dioxide is injected in the blood vessel, typically into the renal artery for renal angiography. This produces a negative contrast compared to usual radiocontrasts. Carbon dioxide gets rapidly absorbed into the blood and there is no adverse effect, though the visualisation is not as good as other radiocontrast agents.
Can psychological stress cause cardiac arrhythmia?
Many of the cardiac arrhythmias can be worsened with psychological stress. During psychological stress, the stress related hormones (e.g. adrenaline, a catecholamine) is released into the blood stream. This is due to activation of the sympathetic nervous system. Catecholamines can enhance the irritability of the heart and increase the chance of abnormal heart rhythm. There are certain heart rhythm disorders which can be specifically worsened by stress. These include certain varieties of long QT syndromes and a rare condition known as catecholaminergic polymorphic ventricular tachycardia. In these conditions, sudden psychological stress can even be life threatening. Stress can also worsen myocardial oxygen demand and worsen blood supply to regions of heart already suffering ischemia (reduced blood supply) and cause cardiac arrhythmia.