Cardiac treadmill testing When patients have difficulties with exercise.it is logical to test them during exercise as well as at rest.The cardiac treadmill is an exarple of such a test and is widely carried out for people with chest pain sugzestive of myocardial ischaemia (inadequate circulation to the beating heart so that painful products of metaholism accumulate).It can also belp in the evaluation of abnormal heart rhythas (experienced by patients as abnormal heart movements -palpitations)and heart failure.However.there are certain conditions where such a test would be un justifiably dangerous and such conditions must be carefully excluded hefore the test is undertaken.Examples are severe hypertension (systolic pressure above 200 mlg.diastolic above 100 mrlig)where the load on the heart would be excessive,and severe narrowing of the aortic valve at the outlet of the heart,or severe heart failure at rest where the ability of the heart to increase its output would be seriously impaired. In preparation for the test,the patient has adhesive electrodes placed on the front of the chest to record,nore or less,the usual 12-lead electrocardiogram. The arms and legs have to be kept free for nowement,although a blood pressure cuff is placed on ome arm to record blood pressure during the test.As the test progresses, the speed and inclination of the treadmill are increased,very gradually for a relatively frail patient and more quickly for someone without serious exercise limitation.The electrocardiogram is recorded continuously and the blood pressure measured at intervals. Information from the electrocardiogran is analysed automatically to display the situation of its ST segment.This segsent is recorded during the plateau phase of the ventricular mocardiun when there is little change in voltage across the merhranes of the cardiac cells.The segment is mormally isoelectric it shows zero voltage and follows the same horizontal line as the segment between the P wave and the 0R5 complex,and,for a longer time,between the T wave and the next P wave. If the segneat is slightly above (tI m)or slightly below (-I rn)the isoelectric
Cardiac treadmill testing When patients have difficulties with exercise, it is logical to test them during exercise as well as at rest. The cardiac treadmill is an example of such a test and is widely carried out for people with chest pain suggestive of myocardial ischaemia (inadequate circulation to the beating heart so that painful products of metabolism accumulate). It can also help in the evaluation of abnormal heart rhythms (experienced by patients as abnormal heart movements - palpitations) and heart failure. However, there are certain conditions where such a test would be unjustifiably dangerous and such conditions must be carefully excluded before the test is undertaken. Examples are severe hypertension (systolic pressure above 200 mmHg, diastolic above 100 mmHg) where the load on the heart would be excessive, and severe narrowing of the aortic valve at the outlet of the heart, or severe heart failure at rest where the ability of the heart to increase its output would be seriously impaired. In preparation for the test, the patient has adhesive electrodes placed on the front of the chest to record, more or less, the usual 12-lead electrocardiogram. The arms and legs have to be kept free for movement, although a blood pressure cuff is placed on one arm to record blood pressure during the test. As the test progresses, the speed and inclination of the treadmill are increased, very gradually for a relatively frail patient and more quickly for someone without serious exercise limitation. The electrocardiogram is recorded continuously and the blood pressure measured at intervals. Information from the electrocardiogram is analysed automatically to display the situation of its ST segment. This segment is recorded during the plateau phase of the ventricular myocardium when there is little change in voltage across the membranes of the cardiac cells. The segment is normally isoelectric - it shows zero voltage and follows the same horizontal line as the segment between the P wave and the QRS complex, and, for a longer time, between the T wave and the next P wave. If the segment is slightly above (+1 mm) or slightly below (-1 mm) the isoelectric
line,this is within normal limits.However,if the segment drops markedly below the line,this constitutes ST depress/oo and is strong evidence that the ayocardium is suffering at that moeent froa ischaemia.A value of -3 m is taken as the threshold for definite ischaemia.Usually,a number of the leads recorded close to the mocardium (V-Va)will show sinilar values.When a patient,at the sane time.experiences the typical chest pain of cardiac ischaemia,the diagmosis is further reinforced.The importance of this finding is that the patieat should them be investigated further.e.g.by visualizing the lumen of the coronary arteries radiologically,and,as necessary,have a procedure to reopen or bypass seriously narrowed vessels. A further significant finding during the treadnill test is an abnormal rhytha, which may account for symptons of palpitations and faintness during exercise. The blood pressure measurenents help to alert the observers to a serious rise in pressure.but,more importantly froa a diagnostic point of view,they may reveal an abnormally low pressure,indicating cardiac failure.During dynamic exercise, such as on a treadnill.the normal heart must increase the force of its ejection of blood,and thus the systolfe pressure rises.In a fit individual exercising strenuously.a systolic pressure of 200 mrHg would not be unusual.Bowever.if the systolie pressure fails to rise,and particularly if it falls during exereise,this is strong evidence of cardiac weakness. A striking feature of the test is that the most dranatic changes may occur in the recovery period,after the patient has stopped exercising.The metaholic 'debts'of the exereise period contine to place a strong demand on the heart,and signs of ischacmia,abeormal rhythms and low blood pressure may appear and persist for a considerable time.This recovery effect is not unknown in normal athletes who have a big debt to repay after a maximal effort and may.in some cases,suffer a degree of post-exercise hypotension.In fact.the test is not without risk for the cardiac patient,but when the information is vital for management decisions,the risk aust be taken.On the other hand,if someone has chest pain leading to anxieties
line, this is within normal limits. However, if the segment drops markedly below the line, this constitutes ST depression and is strong evidence that the myocardium is suffering at that moment from ischaemia. A value of -3 mm is taken as the threshold for definite ischaemia. Usually, a number of the leads recorded close to the myocardium (V1-V6) will show similar values. When a patient, at the same time, experiences the typical chest pain of cardiac ischaemia, the diagnosis is further reinforced. The importance of this finding is that the patient should then be investigated further, e.g. by visualizing the lumen of the coronary arteries radiologically, and, as necessary, have a procedure to reopen or bypass seriously narrowed vessels. A further significant finding during the treadmill test is an abnormal rhythm, which may account for symptoms of palpitations and faintness during exercise. The blood pressure measurements help to alert the observers to a serious rise in pressure, but, more importantly from a diagnostic point of view, they may reveal an abnormally low pressure, indicating cardiac failure. During dynamic exercise, such as on a treadmill, the normal heart must increase the force of its ejection of blood, and thus the systolic pressure rises. In a fit individual exercising strenuously, a systolic pressure of 200 mmHg would not be unusual. However, if the systolic pressure fails to rise, and particularly if it falls during exercise, this is strong evidence of cardiac weakness. A striking feature of the test is that the most dramatic changes may occur in the recovery period, after the patient has stopped exercising. The metabolic 'debts' of the exercise period continue to place a strong demand on the heart, and signs of ischaemia, abnormal rhythms and low blood pressure may appear and persist for a considerable time. This recovery effect is not unknown in normal athletes who have a big debt to repay after a maximal effort and may, in some cases, suffer a degree of post-exercise hypotension. In fact, the test is not without risk for the cardiac patient, but when the information is vital for management decisions, the risk must be taken. On the other hand, if someone has chest pain leading to anxieties
about the heart,then the ahility to exercise up to a high level without any ahnormalities being detected is strongly reassuring
about the heart, then the ability to exercise up to a high level without any abnormalities being detected is strongly reassuring