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Interpretation of computerised exercise stress test in symptomatic subjects referred for cardiac evaluation

Pravin N Soni^1*, Kulkarni D A²

¹Associate Professor, Department of Medicine, IIMS and R Warudi, Jalna, Maharashtra, INDIA.

²Medical Office, Vaijpur, Aurangabad, Maharashtra, INDIA.

Email: dilipk.63@gmail.com, drpravinsoni18@gmail.com

Research Article

 

Abstract               Introduction: Coronary artery disease (CAD) is one of the common causes of morbidity and mortality all over the world. Its first clinical manifestation is acute myocardial infarction or sudden death .which has evolved slowly over many years without notable clinical manifestations. Detection of its presence at an early stage is essential in order to slow the evolution of disease. The value of electrocardiographic stress test as a non-invasive screening procedure for early detection of asymptomatic coronary heart disease or ischemia. Aims and Objectives: The present study was carried out in the department of medicine Government medical college and Hospital, Aurangabad to analyze the computerized stress test for – ischemia. Material and Methods: Patient referred for any reason included in study. A detailed history with clinical examination was carried out according to proforma. Computerized Treadmill Schiller’s Cardiovit CS-200 system was used for exercise test. Summary and Conclusions: Out of 100; 17 subjects grouped as positive test group having ST depression. 83 subjects who had no ST depression grouped together as negative test group. Amongst the ECG parameters, as duration of ST segment depression, time of onset of ST segment depression, leads showing ST segment depression, ‘R’ wave amplitude, QTc interval were significantly associated with a positive stress test, said to have coronary artery disease. Non-ECG parameters were significantly associated with positive stress test and parameters as delta heart rate, heart rate had no relation with the positivity of stress test.

Keyword: Computerized Stress Test.

 

INTRODUCTION

Coronary artery disease (CAD) is one of the common causes of morbidity and mortality all over the world. Frequently its first clinical manifestation is acute myocardial infarction or sudden death the result of advanced coronary arteriosclerosis, which has evolved slowly over many years without notable clinical manifestations. Detection of its presence at an early stage is essential in order to slow the evolution of disease by such preventive measures as diet, exercise, drug therapy (Bellet S, 1967) In the light of these considerations, a simple, objective means of detecting latent coronary artery disease is of utmost importance. With the advent of graded exercise testing and selective coronary arteriography , identification of the patient with the severe coronary artery disease who is at risk for a major cardiovascular event has become a prime diagnostic goal By delineating advanced degrees of coronary disease, coronary arteriography has proved to be one means by which future coronary events might be predicted, the inconvenience, expense and potential danger of this invasive procedure, however, militate its use, as a selective procedure (Goldschlager N et al, 1976) Prognostication of coronary events from response to exercise (stress) testing therefore seems a reasonable alternative. The electrocardiographic exercise test is the most easily applicable and frequently used method available today in the diagnosis of latent coronary heart disease Modern stress testing is based upon the empirical discovery that exercise in patients with coronary artery disease (CAD) produces ST segment depression. The discovery might be credited to Bousfield in 1918 Master and oppenheimer (1929) published first paper on exercise test in 1929. Rober Bruce of seatle made the greatest contribution to the technique of stress testing whose protocol is the standard in most laboratories in the United States. Many other workers made major contributions to the understanding of stress testing (Ellestad M 2003) The value of electrocardiographic stress test as a non-invasive screening procedure for early detection of asymptomatic coronary heart disease is well established with a variable sensitivity and specificity depending upon criterion taken. The exercise electrocardiographic test undergone extensive modifications with the increase in knowledge of the disease and progress in medical instrumentation, which includes the application of computer technology towards evaluation of the electrocardiographic signals (Ellestad M 2003) The interpretation of stress testing has been largely quantitative the principle aim of the procedure being the production of myocardial ischemia, and by implication, the diagnosis of coronary artery disease. Despite criticism, the exercise test remains widely used in the evaluation of chest pain syndromes. The present study designed to analyse the various ECG and non-ECG parameters and their usefulness in interpretation of exercise test

 

AIMS AND OBJECTIVES

The present study was carried out in the department of medicine Government medical college and Hospital, Aurangabad to analyse the computerized stress test for –

1. The incidence of inducible and reversible ischaemia
2. The significance of various other parameters in the diagnosis of ischemia in interpretation of exercise test-

ECG Parameters

1. Time of onset of ST segment depression
2. Duration of ST segment depression
3. Leads showing ST segment depression
4. R wave amplitude
5. QRS Score (Athen’s Score )
6. QX/QT Ratio
7. QT c interval

Non -ECG Parameters

1. Duration of exercise
2. Double product
3. Delta heart rate
4. Heart rate recovery at end of one minute of exercise
5. Anginal score

 

 

 

MATERIAL AND METHODS

This study was conducted in the Department of Medicine at Government Medical College and Hospital, Aurangabad during the period from September, 2001 to August 2004.

Selection of Subjects

The subjects referred for computerized stress test during the period for various reasons comprised the material for the present study. From these, the subjects were selected according to the criterion given below:

Criterion for exclusion

1. Those having ST-T changes in electrocardiogram recorded at rest.
2. History and/or ECG changes suggestive of myocardial infarction.
3. Receiving medications known to affect heart rate rhythm such as beta-blockers, vasopressor, digitals, thyroid harmones, antiarrhythmic drugs as amiodarone, quinidine, lidocaine, mexilletine, phenytoin, flecainide etc.
4. History suggestive of acute illness as infection, severe anaemia, hyperthyroidism.
5. Subjects with locomotion problems.
6. Having left bundle branch block, left ventricular hypertrophy.
7. Having valvular or congenital heart disease.
8. Having diastolic BP more than 100 mmHg at rest.
9. Not attained at least 85% of target heart rate during exercise.
10. Having significant respiratory disease of any etiology.
11. Having acute myocarditis or pericarditis.
12. Those diagnosed to have cardiomyopathy.
13. Subjects with cardiac failure.
14. Subjects with ventricular of atrial arrhythmias at the time of test.

 

STATISTICAL ANALYSIS

The parameters were compared between positive and negative test groups. Statistical analysis was performed using Chi-square test. Chi square analysis with Yate’s correction was also used to evaluate 2 by 2 contingency tables. Differences were considered significant at a ‘p’ value of < 0.05.

 

OBSERVATIONS AND RESULTS

The present study comprised of 100 subjects who underwent computerized stress test (CST) of Government Medical College and Hospital, Aurangabad during the period from September 2001 to August 2004. Those who fulfilled the criteria for inclusion and achieved at least 85% of target heart rate (THR) were only included for the analysis. Of these 100 subjects, 17 subjects who had ST segment depression of 2.00 mm or more were taken positive for CST and comprised test “positive group” and the rest 83 subjects who had no ST segment depression or ST segment depression of less than 2.00 mm comprised the “negative group”. Various parameters were then analysed and compared between these two groups.

Table 9: Distribution of subjects according to change in r-wave amplitude

              (Figures in bracket indicate percentage)

Table 10: Distribution of subjects according to heart rate recovery at the end of one minute of exercise

Heart rate recovery at the end of one minute of exercise	Positive Test Group (n=17)	Negative Test Group (n=83)	Total (n=100)
< 18	02 (11.76)	08 (9.63)	10
>18	18 (88.23)	75 (90.35)	90

(Figures in bracket indicate percentage)

 

Thus, from the present study we recommend that while interpreting stress test, apart from ST segment changes, still considered as gold standards, analysis of additional parameters may be useful for the diagnosis and probably prognosticating coronary events in future.

 

DISCUSSION

Coronary artery disease (CAD) Is one of the common causes of morbidity and mortality all over the world .The detection of disease when it becomes symptomatic is easy but in most of the individuals it remains asymptomatic before manifesting as a catastrophy. The value of electrocardiographic stress test as a non-invasive procedure for early detection of asymptomatic coronary artery disease is well established with a variable sensitivity and specificity depending upon criteria taken (Ellestad M,2003) Exercise stress testing has received much attention in recent years with the principal focus of interest being its predictive power. Among asymptomatic individuals, those with an abnormal ECG response during exercise have a substantial higher risk of developing manifest coronary heart disease then those with a normal ECG response In the present study 100 subjects underwent routine exercise. Only those subjects, who had no ST changes at resting ECG, no history of myocardial infarction, ischemic heart disease arrhythmia, no any cardiovascular, pulmonary disease and who attained target heart rate of at least 85% of predicted maximal heart rate, were selected under study, which included 100 subjects

 

 

 

 

ACKNOWLEDGEMENT

It is a matter of great pleasure to express my sincere regards to Dr. A.B. Solpure sir Dean, IIMSandR for permitting to carry out this study and for his invaluable guidance, critical evaluation and inspiration. I am extremely thankful to Dr. P.Y. Muley, My P.G. teacher. I also wish to express my thanks to Dr. P.L. Bhanap (Professor and HOD, Department of OBGY).

 

REFERENCES

1. Bellet S: The electrocardiogram during exercise as recorded by electrocardiograph. Comparison with the post –exercise electrocardiogram (masters two step test ). Am..J. Carcdiol.18: 385, 1961.
2. Bellet S and Roman L : The exercise test in diabetic patients as studied by electrography. Circulation. 36: 245-67, 1967.
3. Bruce R: Electrocardiographic responses to maximal exercise in American and Chinese population samples, In Blackburn H. (ed ) :Measurement in exercise electrocardiography. Thomas C Springfield, IL 1969
4. Bruce R: Evaluation of functional capacity and exercise tolerance of cardiac patients. Med Concepts Cardiovsc . Dis. 25,321,1956:
5. Bruce R And McDoungh J: Stress testing in screening for cardiovascular disease. Bull. N.Y. Acod. Med.2^nd scr.45 :1288,1969
6. Ellestad M : Stress Testing ,Principles and practice.Ed 5,Oxford University Press , 2003
7. Ellestad M Schrager B: The importance of blood pressure measurement during exercise testing. Cardiovascular Rev Rep 4(3) :381, 1983
8. Goldschlagar N, Selzur A and Cohn K: Treadmill stress test as indicators of presence and severity of coronary artery disease. Annals Of Internal Medicine, 85: 277-286,1976
9. Schiller A: ECG Mesurements and interpretation programs. Jan 1997.

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