from january 1998 to december 2005 , 617 consecutive patients who recently survived an st - segment elevation mi ( > 40 days ) were referred to the cardiac rehabilitation and prevention center of tung wah hospital ( 18,19 ) . this is the largest rehabilitation facility in hong kong and serves a population of about half a million . during this study period , coronary revascularization was performed in those who survived st - segment elevation mi and who experienced chest pain or ischemia inducible on treadmill testing . patients were excluded from this study if they had a positive exercise stress test suggestive of residual myocardial ischemia , documented ventricular tachyarrhythmia that necessitated aicd implantation for secondary prevention , new york heart association ( nyha ) functional class iv , and/or other terminal illness . in hong kong , prophylactic implantation of aicd to prevent sudden cardiac death based on the second multicenter automatic defibrillator implantation trial ii criteria ( 20 ) is not reimbursable and thus is not available in public hospitals ( 16 ) . as a result this was a single - center , prospective observational study , and the local research ethics committee approved the study protocol . following recruitment to the cardiac rehabilitation program , data pertaining to the index mi , demographics , cardiovascular risk factors , and medications were entered into the tung wah hospital cardiac rehabilitation program database . all patients underwent baseline exercise stress tests and echocardiography and were prospectively followed up in our cardiac outpatient clinic . all of the patients were followed up in our cardiac rehabilitation program once every 3 months . deaths within the follow - up period were retrieved from the medical records and discharge summaries and classified according to the modified hinkle - thaler scheme ( 21,22 ) . specifically , sudden cardiac death was defined as a death that occurs within 1 h of onset of cardiac symptoms in a person without any previous condition that would explain the fatality . survival data were also obtained from the hong kong births and deaths general register office . the survival rate , cause of death , and clinical characteristics were compared between patients with and without dm . statistical comparisons were performed using student t test or fisher exact test , as appropriate . kaplan - meier survival analysis with the log - rank test and simple cox regression analysis were used for cumulative incidences of all - cause death , cardiovascular death , sudden cardiac death , and nonsudden cardiac death . multiple cox regression analyses were performed with an enter regression model in which each variable with a p value 0.1 ( based on the univariate analysis ) was entered into the model . from january 1998 to december 2005 , 617 consecutive patients who recently survived an st - segment elevation mi ( > 40 days ) were referred to the cardiac rehabilitation and prevention center of tung wah hospital ( 18,19 ) . this is the largest rehabilitation facility in hong kong and serves a population of about half a million . during this study period , coronary revascularization was performed in those who survived st - segment elevation mi and who experienced chest pain or ischemia inducible on treadmill testing . patients were excluded from this study if they had a positive exercise stress test suggestive of residual myocardial ischemia , documented ventricular tachyarrhythmia that necessitated aicd implantation for secondary prevention , new york heart association ( nyha ) functional class iv , and/or other terminal illness . in hong kong , prophylactic implantation of aicd to prevent sudden cardiac death based on the second multicenter automatic defibrillator implantation trial ii criteria ( 20 ) is not reimbursable and thus is not available in public hospitals ( 16 ) . as a result this was a single - center , prospective observational study , and the local research ethics committee approved the study protocol . following recruitment to the cardiac rehabilitation program , data pertaining to the index mi , demographics , cardiovascular risk factors , and medications were entered into the tung wah hospital cardiac rehabilitation program database . all patients underwent baseline exercise stress tests and echocardiography and were prospectively followed up in our cardiac outpatient clinic . all of the patients were followed up in our cardiac rehabilitation program once every 3 months . deaths within the follow - up period were retrieved from the medical records and discharge summaries and classified according to the modified hinkle - thaler scheme ( 21,22 ) . specifically , sudden cardiac death was defined as a death that occurs within 1 h of onset of cardiac symptoms in a person without any previous condition that would explain the fatality . survival data were also obtained from the hong kong births and deaths general register office . the survival rate , cause of death , and clinical characteristics were compared between patients with and without dm . statistical comparisons were performed using student t test or fisher exact test , as appropriate . kaplan - meier survival analysis with the log - rank test and simple cox regression analysis were used for cumulative incidences of all - cause death , cardiovascular death , sudden cardiac death , and nonsudden cardiac death . multiple cox regression analyses were performed with an enter regression model in which each variable with a p value 0.1 ( based on the univariate analysis ) was entered into the model . a total of 610 post - mi patients with negative exercise stress test were recruited , of whom 236 patients ( 38.7% ) had dm at the time of mi , and 374 did not ( 61.3% ) . compared with nondiabetic patients , patients with dm were older ( 66.2  9.9 vs. 64.1  12.2 years ; p = 0.02 ) and more likely to be female ( 31.8 vs. 21.7% ; p < 0.01 ) , hypertensive ( 63.6 vs. 45.2% ; p < 0.01 ) , have significant renal impairment as defined by serum creatinine level 2 times the upper limit of normal ( 14.1 vs. 5.1% ; p < 0.01 ) , and on statin ( 78.8 vs. 71.1% ; p = 0.04 ) . with regard to the index mi , there was no significant difference in the site of mi , peak creatine kinase level , or proportion of patients undergoing revascularization ( percutaneous coronary intervention or coronary artery bypass grafting ) . nonetheless , post - mi patients with dm had a lower left ventricular ejection fraction ( lvef ) ( 44.6  10.5 vs. 46.2  10.0% ; p = 0.04 ) , and a lower proportion was classified as nyha function class i ( 39.8 vs. 53.5% ; p < 0.01 ) compared with post - mi patients without dm . baseline characteristics of patients with and without dm after a mean follow - up of 62.7  43.9 months ( range 0.2148.6 months ) , 67 patients with dm ( 28.4% , 6.2%/year ) and 76 patients without dm ( 20.2% , 3.6%/year ) had died . figure 1a depicts the kaplan - meier curves for the percentage of patients with and without dm who survived . for those patients with dm , the proportion that died during follow - up was significantly higher than for those without dm : hazard ratio ( hr ) 1.74 ( 95% ci : 1.282.56 ; p < 0.001 ) . of these 143 deaths , 66 ( 46.2% ) were attributed to a cardiac cause , of which sudden cardiac death accounted for 66.7% . the proportion of patients with dm who died resulting from a cardiac cause was higher than for those without dm ( 32 of 236 [ 3.0%/year ] vs. 34 of 374 [ 1.6%/year ] , hr : 1.84 [ 95% ci : 1.163.21 ] ; p = 0.01 ) ( fig . likewise , and more importantly , the incidence of sudden cardiac death was also higher in patients with dm ( 23 of 236 [ 2.1%/year ] vs. 21 of 374 [ 1.0%/year ] , 2.14 [ 1.224.23 ] ; p < 0.001 ) ( fig . there was no statistically significant difference in the nonsudden cardiac death rate between the two groups ( 9 of 236 [ 0.8%/year ] vs. 13 of 374 [ 0.6%/year ] , 1.36 [ 0.573.36 ] ; p = 0.47 ) ( fig . kaplan - meier curves of all - cause death ( a ) , cardiac death ( b ) , sudden cardiac death ( c ) , and nonsudden cardiac death ( d ) in patients with and without dm . to identify risk factors that could predict sudden cardiac death , patients were categorized as follows : 1 ) those with sudden cardiac death ( n = 44 ) or 2 ) those without sudden cardiac death ( n = 566 ) . table 2 summarizes their baseline clinical characteristics . there were no statistically significant differences in age and sex between the two groups . in the sudden cardiac death group , there was a higher proportion of patients with dm ( 52.3 vs. 37.6% ; p = 0.05 ) , a lower proportion of hypercholesterolemia defined as fasting ldl cholesterol level 2.6 mmol / l or already on pharmacological treatment for hypercholesterolemia ( 40.9 vs. 57.6% ; p = 0.03 ) , and a lower proportion of patients with nyha class i ( 22.7 vs. 50.2% ; p < 0.01 ) ; they were also less likely to have received percutaneous coronary intervention ( 29.5 vs. 58.0% ; p < 0.01 ) or statin therapy ( 59.1 vs. 75.3% ; p = 0.02 ) . nonetheless , there were no significant differences in other demographics , medications , or site of index mi . multiple cox regression analysis revealed that only dm ( adjusted hr : 1.9 [ 95% ci : 1.043.40 ] ; p = 0.04 ) , lvef 30% ( 3.6 [ 1.468.75 ] ; p < 0.01 ) , and nyha class > ii ( 4.2 [ 1.879.45 ] ; p baseline characteristics of patients with or without sudden cardiac death as lvef was a major determinant of future sudden cardiac death in this cohort , and current guidelines are based largely on lvef for aicd prescription ( 23 ) , we further evaluated the effect of dm on sudden cardiac death in patients with different levels of lvef . among patients with lvef 30% ( n = 68 ) , there was no statistically significant difference in the proportion of sudden cardiac death between those with and without dm ( hr : 0.34 [ 95% ci : 0.131.14 ] , p = 0.09 ) ( fig . figure 2a depicts the kaplan - meier curves for these patients . on the contrary , among patients with lvef between 31 and 50% ( n = 348 ) and those with lvef > 50% ( n = 194 ) , there was a higher proportion of sudden cardiac death among those with dm ( 12 of 129 vs. 10 of 219 ; hr : 2.30 [ 95% ci : 1.086.91 ] ; p = 0.03 [ fig . 2b ] ; and 8 of 73 vs. 1 of 121 ; 14.90 [ 2.7542.90 ] ; p < 0.01 [ fig . 2c ] ) . overall , the 5-year sudden cardiac death rates in patients with dm did not differ significantly in relation to lvef : lvef 30% , lvef 3150% , and lvef > 50% ( 8.8 vs. 7.8 vs. 6.8% , respectively ; p = 0.83 ) . kaplan - meier curves of sudden cardiac death among patients with and without dm and with lvef 30% ( n = 68 ) ( a ) , lvef 3150% ( n = 348 ) ( b ) , and lvef > 50% ( n = 194 ) ( c ) . as lvef was a major determinant of future sudden cardiac death in this cohort , and current guidelines are based largely on lvef for aicd prescription ( 23 ) , we further evaluated the effect of dm on sudden cardiac death in patients with different levels of lvef . among patients with lvef 30% ( n = 68 ) , there was no statistically significant difference in the proportion of sudden cardiac death between those with and without dm ( hr : 0.34 [ 95% ci : 0.131.14 ] , p = 0.09 ) ( fig . figure 2a depicts the kaplan - meier curves for these patients . on the contrary , among patients with lvef between 31 and 50% ( n = 348 ) and those with lvef > 50% ( n = 194 ) , there was a higher proportion of sudden cardiac death among those with dm ( 12 of 129 vs. 10 of 219 ; hr : 2.30 [ 95% ci : 1.086.91 ] ; p = 0.03 [ fig . 2b ] ; and 8 of 73 vs. 1 of 121 ; 14.90 [ 2.7542.90 ] ; p < 0.01 [ fig . overall , the 5-year sudden cardiac death rates in patients with dm did not differ significantly in relation to lvef : lvef 30% , lvef 3150% , and lvef > 50% ( 8.8 vs. 7.8 vs. 6.8% , respectively ; p = 0.83 ) . kaplan - meier curves of sudden cardiac death among patients with and without dm and with lvef 30% ( n = 68 ) ( a ) , lvef 3150% ( n = 348 ) ( b ) , and lvef > 50% ( n = 194 ) ( c ) . we show that despite the lack of residual myocardial ischemia , post - mi patients with dm had a higher incidence of all - cause mortality , cardiac death , and sudden cardiac death , but not nonsudden cardiac death , compared with post - mi patients without dm . this was in addition to the two most recognized risk factors for sudden cardiac death in post - mi patients : low lvef and poor functional class . more importantly , the increased risk of sudden cardiac death post - mi in patients with dm remained across different levels of lvef . published data concerning the contribution of dm to sudden cardiac death nonetheless remain conflicting . in previous epidemiological studies , patients with dm but no previously documented coronary artery disease appeared to be at higher risk of sudden cardiac death , with an hr ranging from 1.82 to 4.22 ( 11,2426 ) . in contrast , among studies that did not exclude patients with pre - existing coronary artery disease ( 2730 ) , the association between dm and sudden cardiac death remained equivocal . this could be partly related to the heterogeneity in the study populations : it has been postulated that the competing risks for sudden cardiac death related to coronary artery disease and other associated factors in these populations outweighed the increased risk related to dm ( 31 ) . 10 ) reported the outcome following 5-year follow - up of a cohort of 3,267 patients who survived acute mi . the incidence of sudden cardiac death was higher in patients with dm than those without dm , with an adjusted hr of 2.3 ( 10 ) . this increased risk of sudden cardiac death remained in multiple logistic regression analysis . nonetheless , because the study did not exclude patients with residual myocardial ischemia , it remained unclear whether the increased sudden cardiac death in patients with dm was the result of an arrhythmic event , residual ischemia , or both . this is because , although sudden cardiac death can be considered primarily an arrhythmic event , post - mi patients with dm may have significant residual ischemia even after revascularization therapy ( 32 ) that is conducive to developing a life - threatening ventricular tachyarrhythmia . in the current study , this indicated the absence of significant residual myocardial ischemia ; nonetheless , the risk of sudden cardiac death remained higher in these post - mi patients with dm compared with those without . more importantly , the risk of sudden cardiac death was remarkably consistent with the study by junttila et al . ( hr : 2.3 ) ( 10 ) and the current study ( 2.14 ) . this further supports the undeniable risk of sudden cardiac death post - mi associated with dm . the effectiveness of prophylactic aicd therapy to reduce sudden cardiac death in post - mi patients without a history of cardiac arrest or ventricular tachyarrhythmias has been established by major clinical trials ( 20 ) . current guidelines thus recommend the therapy for primary prevention of sudden cardiac death in post - mi patients with low lvef ( 23 ) . unfortunately , most post - mi patients who fulfill these criteria for aicd therapy will not receive aicd implantation in most countries due to reimbursement difficulties ( 16 ) . the ability to triage patients at high risk of sudden cardiac death using clinical parameters in addition to standard indications for aicd therapy may allow for more cost - effective use of such therapy . more importantly , although low lvef is the major criteria for prophylactic aicd therapy in post - mi patients , our study and that of junttila et al . ( 10 ) have demonstrated that the risk of sudden cardiac death remains substantial in diabetic patients with lvef well above the conventional threshold for prophylactic aicd therapy . first , it was limited by the relatively small sample size and a single - centered observational design . second , given the nature of the study , plausible mechanisms for dm - related sudden cardiac death such as cardiac autonomic dysfunction ( 13,28,33 ) , qt prolongation ( 34,35 ) , as well as severe hypoglycemia secondary to stringent glycemic goal ( 15,36 ) were not addressed . third , the development of new coronary lesions and their identification during the study period was not specifically addressed . ideally , the coronary artery disease severity should have been assessed both at baseline and throughout the study period in all of the participants , using , for example , a modified gensini index . unfortunately , in the current study , reevaluation of coronary angiography would only be performed on a clinical basis in patients with recurrence ischemic symptom rather than on a routine basis . this study nonetheless demonstrates that baseline dm state predicted incident sudden cardiac death following mi in a cohort of chinese patients who were free of significant myocardial ischemia . further studies are needed to define the recommendations for risk stratification and therapy , including implantation of a cardioverter defibrillator device , in this particularly high - risk group . first , it was limited by the relatively small sample size and a single - centered observational design . second , given the nature of the study , plausible mechanisms for dm - related sudden cardiac death such as cardiac autonomic dysfunction ( 13,28,33 ) , qt prolongation ( 34,35 ) , as well as severe hypoglycemia secondary to stringent glycemic goal ( 15,36 ) were not addressed . third , the development of new coronary lesions and their identification during the study period was not specifically addressed . ideally , the coronary artery disease severity should have been assessed both at baseline and throughout the study period in all of the participants , using , for example , a modified gensini index . unfortunately , in the current study , reevaluation of coronary angiography would only be performed on a clinical basis in patients with recurrence ischemic symptom rather than on a routine basis . this study nonetheless demonstrates that baseline dm state predicted incident sudden cardiac death following mi in a cohort of chinese patients who were free of significant myocardial ischemia . further studies are needed to define the recommendations for risk stratification and therapy , including implantation of a cardioverter defibrillator device , in this particularly high - risk group .
objectivediabetes mellitus ( dm ) is a well - established risk factor for coronary artery disease . 
 nonetheless , it remains unclear whether dm contributes to sudden cardiac death in patients who survive myocardial infarction ( mi ) . 
 the objective of this study was to compare the incidence of sudden cardiac death post - mi in diabetic and nondiabetic patients with no residual myocardial ischemia.research design and methodsa total of 610 consecutive post - mi patients referred to a cardiac rehabilitation program with negative exercise stress test were studied.resultsof these , 236 patients had dm at baseline . over a mean follow - up of 5 years , 67 patients with dm ( 28.4% ) and 76 of 374 patients without dm ( 20.2% ) had died with a hazard ratio ( hr ) of 1.74 ( 95% ci : 1.282.56 ; p < 0.001 ) . 
 patients with dm also had a higher incidence of cardiac death ( 1.84 [ 1.163.21 ] ; p = 0.01 ) , principally due to a higher incidence of sudden cardiac death ( 2.14 [ 1.224.23 ] ; p < 0.001 ) . 
 multiple cox regression analysis revealed that only dm ( adjusted hr : 1.9 [ 95% ci : 1.043.40 ] ; p = 0.04 ) , left ventricular ejection fraction ( lvef ) 30% ( 3.6 [ 1.468.75 ] ; p < 0.01 ) , and new york heart association functional class > ii ( 4.2 [ 1.879.45 ] ; p 
 < 0.01 ) were independent predictors for sudden cardiac death . among patients with dm , 
 the 5-year sudden cardiac death rate did not differ significantly among those with lvef 30% , lvef 3150% , or lvef > 50% ( 8.8 vs. 7.8 vs. 6.8% , respectively ; p = 0.83).conclusionspost - mi patients with dm , even in the absence of residual myocardial ischemia clinically , were at higher risk of sudden cardiac death than their non - dm counterparts .