HIGHER NEGATIVE PREDICTIVE VALUE ON SEVEN YEARS FOLLOW UP OF NORMAL GATED MYOCARDIAL PERFUSION IMAGING IN DIABETIC PATIENTS WITH HBA1C ≤7.3% CUTOFF.

Abstract

Purpose: This prospective study was carried out to find negative predictive value (NPV) of normal myocardial perfusion imaging (MPI) in diabetic patients with predefined cut-off value of glycosylated hemoglobin A1c (HbA1c) ≤7.3%.  Methodology: This study was conducted at Karachi Institute of Heart Disease (KIHD) after prior approval from ethical committee. Total 257 diabetic patients who were labeled as normal MPI from June-2011 till March-2012 were included.  These patients were followed on telephone for seven years for cardiac events including fatal myocardial infarction (FMI) and nonfatal myocardial infarction (NFMI). Follow‑up was not available in 33 patients, leaving a cohort of 224 participants. Mean HbA1c was calculated for seven years. Patients were subdivided according to predefined cut-off value of HbA1c 7.3% as determined in previously published study by our group (57 in group A with HbA1c >7.3% and 167 in group B with HbA1c ≤ 7.3%). Results: No statistically significant difference was found in age, gender, body mass index, hypertension, dyslipidemia, family history, LV function, Bruce and vasodilator stress protocol in both groups except metabolic equivalent of task (METS) was significantly higher in group B (<0.05). Overall mean survival was significantly higher in group B with HbA1c ≤7.3 (Mean=80 vs. 71; CI=78-83 vs. 64-78 months in Group B and A respectively; log rank value=5.576; p <0.05). Significantly higher fatal and non-fatal cardiac events on seven years follow up were recorded in group A with HbA1c >7.3% with lower METS <7 (3 vs. 0 FMI and 11 vs. 9 NFMI and annualized event rate 0.75% vs. 0% and 2.8% vs. 0.76% group A and Group B respectively; p<0.05). Conclusion:  We conclude that a negative MPS has a significantly higher NPV and better effort tolerance in diabetics with good glycemic control (mean HbA1c ≤ 7.3%) than diabetics with impaired glycemic control (mean HbA1c >7.3%). Impaired glycemic control is supposed to be associated with impaired endothelial function and demands a correlative study in future.

Key word: Gated myocardial perfusion imaging; diabetics; HbA1C; METS, fatal MI; non-fatal MI.