RESUMEN
To evaluate the validity of exercise tolerance test [ETT] with treadmill exercise in the diagnosis and follow-up of ischaemic heart disease [IHD], taking myocardial perfusion scan [MPS] as standard. Retrospective, validation study. Nuclear Medical Centre [NMC] Armed Forces Institute of Pathology [AFIP], Rawalpindi, Pakistan, from 1 January to 31 December 2009. One hundred and nineteen patients [88 males, 31 females], referred for MPS; were selected through non-probability, consecutive sampling. Patients of all ages and gender, fit to undertake treadmill exercise, were included. Patients with contraindications to ETT, like unstable angina, conduction abnormalities, etc., or those who had taken a beta blocker within the preceding 24 hours, were excluded. ETT through treadmill exercise was done, followed by MPS with single photon emission computed tomography [SPECT] technique, using Thallium-201 or Technetium-99 m 2-methoxy-isobutyl-isonitrile [MIBI]. ETT was interpreted as positive or negative for ischaemia, with borderline changes considered positive. MPS was interpreted as positive or negative for ischaemia. Validity of ETT was evaluated in terms of sensitivity [Sn], specificity [Sp], and positive and negative predictive value [PPV and NPV], taking MPS as standard. Sensitivity of ETT was found to be 77.5% and specificity was 43.6%. PPV was 73.8% and NPV was 48.6%. Out of a total [n] of 119 patients, true positive [TP] cases were 62, true negative [TN] 17, false positive [FP] 22 and false negative [FN] 18. ETT is an acceptably sensitive but non-specific test for evaluating myocardial ischaemia, with adequate PPV but low NPV, when validating it against MPS. Replacing the MPS with ETT, in the diagnosis and follow-up of IHD, is thus, not prudent. ETT can be useful as a screening test
RESUMEN
To evaluate the effect of post-myocardial infarction Streptokinase therapy on myocardial viability, employing Thallium-201 single photon emission computed tomography [TL-201 SPECT]. Retrospective, experimental study. The Nuclear Cardiology Department, Armed forces Institute of Cardiology / National Institute of Heart Diseases, Rawalpindi, from 1[st] April 2009 to 31[st] October 2009. Male patients, who had suffered from acute myocardial infarction [AMI], in an area supplied by the left anterior descending [LAD] artery, had infarct-related electrocardiogram [ECG] changes and received or did not receive Streptokinase therapy, were included. Those with a normal ECG, or history of revascularization, or non-ST elevation MI, or more than on MIs, were excluded. The patients were divided into groups 1 [who received Streptokinase] and 2 [who did not receive Streptokinase]. Each group contained 42 patients and all underwent scintigraphic viability study through intravenous injection of 3.0 mCi [123 MBq] of TL-201, followed by rest-redistribution SPECT imaging on a dual head, dedicated cardiac gamma camera system [Philips Cardio MD [registered sign]]. Emory's cardiac toolbox [registered sign] and AutoQUANT [registered sign] were used for data processing and quantitative estimation of viable myocardium. Empirical scores from 0 to 2 were assigned to each of the scans, in the order of increasing viability, and these were compared across the two groups. Group 1 contained 42 patients [age range = 38 to 80 years, mean = 53.98 +/- 11.26 years], in whom empirical viability scoring was done. Score 0 was seen in 2 patients, score 1 was seen in 15 patients and score 2 was seen in 25 patients from this group. Group 2 also contained 42 patients [age range = 38 to 80 years, mean = 56.71 +/- 9.05 years], in whom viability score of 0 was seen in 3 patients, score 1 was seen in 11 patients and score 2 was seen in 28 patients from this group. Age difference between the two groups was statistically insignificant [p = 0.223]. The myocardial viability results analysed by 3 x 2 contingency table applying chi- square [X[2]] test also showed no significant difference between groups 1 and 2 [p= 0.611]. This study did not find any significant difference in myocardial viability - post- myocardial infarction - in patients who received or did not receive Streptokinase therapy