Myocardial viability, which definition should we depend upon role of radionuclide imaging

Rest-redistribution thallium [RD T1] imaging has high negative predictive value [NPV] but low positive predictive value [PPV] for the prediction of recovery of regional myocardial dysfunction after revascularization [R]. Combining perfusion [MP] and functional data with nitrate-enhanced gazed SPECT MIBI [GSM] at rest appears to be a promising approach for viability detection. Differentiate between the role of resting TL and resting GSM for detection of viability. 66 pts with coronary artery disease [CAD] underwent T1 imaging [R-RD protocol], 2 sets of resting GSM using 2 MIBI injections, and echocardiography, both at rest and after low dose dobutamine [LDD]. One hour Before GSM2, 60 mg. of oral trimetazidine [TMZ] and nitrates had been given. All pts had their echos repeated after [R]. Perfusion and wall motion [WM] were scored from 0 to 4 [absent to normal] using 17 segment model. 385/1122 segments were found to have abnormal resting WM on echo. 165/217 of the hypokinetic segments, 48/102 of the akinetic segments and 6/66 of the dyskinetic segments showed contractile response for LDD echo. The MP images showed normal uptake, complete, partial reversibility and poor uptake in TI, GSM1 and GSM2 images as following: [54, 31, 45], [36, 22, 35], [198, 119, 190] and [32, 148, 50] of segments respectively. Following table showed degree of matching. Sensitivity and specificity of T1, GSM1 and GSM2 and LDD echo had been found respectively to be [94.9%, 75.5%], [60%, 93.6%], [94.2%, 90%] and [79.6%, 100%]. Post-revascularization Resting Echocardiography: -, -, Viable, Non-Viable, -, Viable, Non-Viable, -, Viable, Non-Viable, -, Viable, Non-Viable. Pre-revascularization: Viable- Non-Viable, Rest-Redistribution Thallium, 261- 14, 27- 83, Non-TMZ gated SPECT, 165- 110, 7- 103, TMZ gated SPECT, 259- 16, 11- 99, LDD Echocardiography, 219- 56, 0- 110. Total: -, -, 275, 110, -, 275, 110, -, 275, 110, -, 275, 110. Clinical definition of viability is better looked for in GSM2

Comparative study between low dose dobutamine echocardiography and low dose dobutamine gated single photon emission computed tomography [gSPECT] in detection of myocardial viability

The identification of severely dysfunctional but viable myocardium is of particular importance for the selection of patients with depressed left ventricular function who will benefit from coronary revascularization. Assessment of inotropic reserve with dobutamine has recently been used for this purpose. Comparing the accuracy of low-dose dobutamine [LDD] gated myocardial SPECT [gSPECT] with the accuracy of low dose dobutamine echocardiography [DSE] and resting perfusion single photon emission computed tomogra phytomography [SPECT] for the identification of viable myocardium in patients with previous myocardial infarction. Resting and low-dose dobutamine [7.5 micro g/kg/min] gated 99mTc-tetrofosmin gSPECT [TI and T2 respectively] and echocardiography [at rest and during low dose dobutamine] [R and DSE] and resting post-revascularization echocardiography [PRecho] [3 months later] were prospectively studied in 33 patients with previous myocardial infarction and severely depressed regional [function. Revascularization had been done either by CABG or PTCA for all patients. Nitroglycarine had been administered 15 min for all patients before 99m Tc-tetroforminT2. Wall motion assessment was done using 4 point score with 1 normal and 4 dyskinetic and viable tissue was diagnosed by presence of contractile response [CD] during LDD infusion in hoth echocardiography and gated SPECT using 17 segment model. Viability was defined in perfusion study by a relative Uptake 50% of tile maximum uptake. Viability in "SPECT depended upon both end-diastolic [ED] image [perfusion] and End-systolic [ES] [Contractility] images. Out of the 561 myocardial segments resting echo [R] revealed 367 segments with normal wall motion [NWM], 109 hypokinetic with CD in 83, 52 akinetic with CD in 24, 33 dyskinetic with CD in 3. Post-revascularization echo revealed 476 segments with NWM, 26 hypo, 29 ak., and 30 dyskinetic. Concerning gSPECT, out of the 194 segments with abnormal wall motion. T1 and T2 revealed 16 and 23 with normal uptake, 11 and 18 with complete reversibility, 60 and 96 with partial reversibility with overall detection of viability in 44.8%: and 70.% respectively. Degree of matching between DSE and T1 and T2 was found to be 70.6% and 80.9% respectively. Compared to PR echo., degree of matching was 69.6%, 92.3% and 85.6% for TI, T2 and DSE respectively. Pharmacological enhancement for detecting viability either by gSPECT or echocardiography. Combined Perfusion and functional assessment compensates for lower sensitivity of [99m]Tc-tetrofosmin