Sudden cardiac death in diabetes mellitus: risk factors in the Rochester diabetic neuropathy study

The CETP TaqIB polymorphism is associated with the risk of sudden death in type 2 diabetic patients

OBJECTIVE

Type 2 diabetic patients have a high risk of coronary heart disease (CHD) and sudden death. This cardiovascular risk can be partly attributed to low levels of HDL cholesterol. The B2 allele of the CETP TaqIB polymorphism has been repeatedly reported to be associated with high HDL cholesterol levels in both healthy and type 2 diabetic subjects, but its association with CHD is unclear. We investigated the association of the CETP TaqIB polymorphism with CHD, and sudden death in particular, in a prospective cohort of type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

The CETP TaqIB polymorphism was genotyped in 3,124 type 2 diabetic subjects with high cardiovascular risk: the Noninsulin-Dependent Diabetes, Hypertension, Microalbuminuria, Proteinuria, Cardiovascular Events, and Ramipril (DIABHYCAR) study. We used Cox regression analysis to estimate the impact of the TaqIB single nucleotide polymorphism on the CHD events (myocardial infarction or sudden death) during follow-up.

RESULTS

The incidence of CHD was higher in B1B1 homozygotes than in B2 carriers (P = 0.02). This effect was mainly due to sudden death (hazard ratio [B1B1 vs. B2+] = 1.51 [95% CI = 1.05-2.18]). Although the B1 allele was associated in a dose-dependent fashion with lower HDL cholesterol (P < 0.001), the association with sudden death persisted after adjustment for multiple risk factors, including HDL cholesterol levels.

CONCLUSIONS

In type 2 diabetic patients, the CETP TaqIB polymorphism is a good genetic predictor of cardiac mortality. This association is partly independent of the effect on HDL cholesterol levels.

Interactions between microvascular and macrovascular disease in diabetes: pathophysiology and therapeutic implications

Convention partitions the complications of diabetes into two main subtypes. First are the diabetes-specific microvascular complications of retinopathy, nephropathy and neuropathy; second are the atherothrombotic macrovascular complications that account for the majority of premature deaths. Pathological interactions between microvascular and macrovascular complications, for example, nephropathy and macrovascular disease, are common. Similar mechanisms and shared risk factors drive the development and progression of both small and large vessel disease. This concept has therapeutic implications. Mounting evidence points to the need for multifactorial strategies to prevent vascular complications in subjects with diabetes and/or the metabolic syndrome. We advocate a combined therapeutic approach that addresses small and large vessel disease. Preferential use should be made of drug regimens that (i) maximize vascular protection, (ii) reduce the risk of iatrogenic vascular damage and (iii) minimize the increasing problem of polypharmacy.

The epidemiology of non-traumatic prehospital sudden death in Macau

OBJECTIVE

To understand the epidemiology of non-traumatic prehospital sudden death (NPSD) in Macau, and to discuss potential diseases related to NPSD.

METHODS

We analysed the epidemiological characteristics of 605 NPSD cases occurred between January 1, 2003 and December 31, 2005 in Macau. Four hundred NPSD victims' medical records were reviewed to collect information regarding associated diseases.

RESULTS

NPSD was more common in males than females (56.5% versus 43.5%). Male patients were 7.9 years younger than female patients (68.8+/-17.7 versus 76.7+/-16.7, p=0.000). NPSD had a higher incidence in the months December to March. There were 21.8 NPSD cases per month on an average during this period. NPSD occurred more frequently during daylight hours. The following diagnoses were frequently found in the patients' medical records: hypertension (39.5%), cerebral vascular accident (18.5%), type 2 diabetes mellitus (17.8%), congestive heart failure (13.3%), chronic renal failure (11.3%), and chronic obstructive pulmonary disease (11%). Coronary artery disease was diagnosed in only 9.2% in all NPSD cases.

CONCLUSIONS

NPSD has similar epidemiological characters with sudden cardiac death. Most NPSD should be presumed to be of cardiac aetiology. Chronic diseases that affect cardiovascular system have close relations with NPSD. Coronary artery disease in these patients should be recognised early.

Increased prevalence of ventricular fibrillation in patients with type 2 diabetes mellitus

Diabetes mellitus (DM) is an independent risk for cardiovascular disease. Furthermore, patients with DM have increased risk for ventricular arrhythmia that is thought to be secondary to coronary artery disease (CAD) or congestive heart failure (CHF). We hypothesized that DM may cause ventricular arrhythmias independent of CAD or CHF. Using a large database, we evaluated the occurrence of ventricular fibrillation in patients with DM adjusting for CAD and CHF. We used patient treatment files (PTF), documents of inpatients' admissions containing discharge diagnoses (ICD-9 codes) from all Veterans Health Administration Hospitals. The patients were stratified in two groups: ICD-9 code for DM (293 124) and a control group with ICD-code for hypertension (HTN) but no DM (552 623). ICD-9 codes for ventricular fibrillation were used for this study. We performed uni- and multivariant analysis adjusting for comorbid conditions. Ventricular fibrillation was present in 563 (0.2%) vs 781 (0.1%) in the control group. Using multivariate analysis, DM remained independently associated with ventricular fibrillation (odds ratio: 1.7; confidence interval: 1.5-1.9; P < 0.000). Patients with DM have significantly higher prevalence of ventricular fibrillation independent of CAD or CHF, which in part may explain the higher risk of sudden death in patients with DM.

Obesity as a risk factor for sustained ventricular tachyarrhythmias in MADIT II patients

BACKGROUND

Obesity, as defined by body mass index > or =30 kg/m(2), has been shown to be a risk factor for cardiovascular disease. However, data on the relationship between body mass index (BMI) and the risk of ventricular arrhythmias and sudden cardiac death are limited. The aim of this study was to evaluate the risk of ventricular tachyarrhythmias and sudden death by BMI in patients after myocardial infarction with severe left ventricular dysfunction.

METHODS

The risk of appropriate defibrillator therapy for ventricular tachycardia or ventricular fibrillation (VT/VF) by BMI status was analyzed in 476 nondiabetic patients with left ventricular dysfunction who received an implantable cardioverter defibrillator (ICD) in the Multicenter Automatic Defibrillator Implantation Trial-II (MADIT II).

RESULTS

Mean BMI was 27 +/- 5 kg/m(2). Obese patients comprised 25% of the study population. After 2 years of follow-up, the cumulative rates of appropriate ICD therapy for VT/VF were 39% in obese and 24% in nonobese patients, respectively (P = 0.014). In multivariate analysis, there was a significant 64% increase in the risk for appropriate ICD therapy among obese patients as compared with nonobese patients, which was attributed mainly to an 86% increase in the risk of appropriate ICD shocks (P = 0.006). Consistent with these results, the risk of the combined endpoint of appropriate VT/VF therapy or sudden cardiac death (SCD) was also significantly increased among obese patients (Hazard Ratio 1.59; P = 0.01).

CONCLUSIONS

Our findings suggest that in nondiabetic patients with ischemic left ventricular dysfunction, a BMI > or =30 kg/m(2) is an independent risk factor for ventricular tachyarrhythmias.

Diabetes as a risk factor for cardiac conduction defects: a review

Diabetes mellitus (DM) is a major risk factor for cardiovascular disease and mortality with increasing prevalence in the ageing population. Coronary artery disease is the major cardiovascular abnormality in DM patients. Cardiomyopathy and left ventricular hypertrophy are two other known associated cardiovascular abnormalities. There are a few non-randomized studies reporting increased prevalence of cardiac conduction abnormalities, such as right bundle branch block (RBBB), bifascicular block and high degree atrioventricular (AV)-block but not left bundle branch block (LBBB), in DM patients. Most clinicians are not aware of this association, and it is rarely mentioned in the published reviews about cardiovascular abnormalities in this population. The cause of cardiac conduction abnormalities in DM patients is not known. If autonomic neuropathy or DM-associated cardiovascular disease plays a role, it remains unknown. The goal of this manuscript is to review the current literature about the risk of conduction abnormalities in DM patients. For this study, Medline, Google and published books were searched and reviewed for any references that matched cardiac conduction abnormalities, AV-block, BBB for bundle branch block, LBBB, RBBB, bifascicular block, autonomic neuropathy and DM.

Coronary heart disease and cardiovascular autonomic neuropathy in the elderly diabetic

Diabetes and old age come together to increase the frequency and severity of coronary heart disease. Often clinically nearly silent, symptoms frequently manifest dramatically, to such an extent that the question of screening should be raised, as in younger subjects. Preventing these manifestations relies on better management of the cardiovascular risk factors and obtaining good blood glucose control, but here progress remains necessary, which also requires adapting to the older patient's clinical and psychological condition. Cardiovascular autonomic neuropathy is a frequent degenerative complication in diabetics, particularly in the oldest subjects. The most severe types have serious clinical consequences, thus a higher mortality factor, but the mechanisms remain poorly understood. As for coronary heart disease, the therapeutic tools have expanded these last few years and should be thought out in relation to the geriatric evaluation, with the objective of improving these patients' quality of life. Therefore, a necessary distinction should be made between subjects who have aged successfully, whose management, ultimately, differs little from younger subjects, and frail elderly individuals for whom exploratory techniques and treatment should be adapted.

Autonomic dysfunction in obstructive sleep apnea is associated with impaired glucose regulation

INTRODUCTION

Autonomic dysfunction has been theorized to be responsible for the increased risk of cardiovascular disease in obstructive sleep apnea (OSA). Previous studies did not control for the presence of impaired glucose regulation (IGR, comprising impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes) which is also associated with abnormalities in autonomic function.

METHODS

Thirty-two patients were recruited for the study. Patients underwent autonomic testing consisting of heart rate response to deep breathing, valsalva maneuver, tilt-up, and quantitative sudomotor axon reflex testing. Polysomnography (PSG) and a 2-h oral glucose tolerance test were performed. Results were analyzed with logistic regression, with age, race, body mass index (BMI), and gender as covariates.

RESULTS

Nineteen of 24 patients with OSA had abnormal glucose (79%, p=0.04) compared to two of nine patients without OSA. The correlation between IGR, OSA and total autonomic dysfunction was similar (p=.10 for IGR, p=0.06 for OSA). However, cardiac autonomic function was more strongly associated with IGR than OSA (p=.10 vs. 0.50). Age was a significant confounder, as glucose correlated with adrenergic autonomic dysfunction significantly when age was removed from the model (p=0.006).

CONCLUSIONS

The presence of IGR may be a confounding factor in studies of autonomic function in OSA. Larger studies are needed to delineate whether OSA is directly associated with autonomic dysfunction or whether the previously described association between dysautonomia and OSA may have been due to glucose dysregulation.

Cardiovascular autonomic neuropathy: diagnosis and management

Cardiovascular autonomic neuropathy increases morbidity and mortality, and reduces quality of life and activities of daily living of the patients with diabetes. The reduced cardiovascular autonomic function as measured by heart rate variability is strongly associated with an increased risk of silent myocardial ischemia and mortality. Currently, no specific therapeutic strategies can be recommended for cardiac autonomic neuropathy, but management of hyperglycemia and the use of angiotensin-converting enzyme inhibitors and beta blockers should be instituted.

[Prognosis of patients admitted in a coronary care unit after resucitating from out-of-hospital sudden cardiac death]

BACKGROUND AND OBJECTIVE

The aims of the present study were to analyze the prognosis after resuscitation from out-of-hospital sudden cardiac death in patients admitted to the coronary care unit, and to identify the predictor variables of morbi-mortality.

PATIENTS AND METHOD

From November 1999 to January 2004 we analyzed 63 patients (47 males) aged 61 +/- 12 years who were admitted to the coronary care unit following successful resuscitation from sudden cardiac death. The clinical and electrocardiographic characteristics were correlated with the mortality and neurological impairment.

RESULTS

Thirty-five patients (55.5%) were discharged, while twenty-eight patients (45.5%) died 28 +/- 4 days after admission, most of them during hospitalization. The main underlying disorder was coronary artery disease (80.9%). When survivors and non-survivors were compared, the variables associated with a worse prognosis were diabetes mellitus (68.4% vs 17.1%, P < .02), the presence of valvular heart disease (28.6% vs 0%, p < 0.003), chronic atrial fibrillation (42.9% vs 14.3%, P < .02) and asystole as the initial rhythm observed (42.9% vs 11.4%, P < .01). Multivariate analysis identified asystole as an independent factor of poor prognosis (P < .02). Death was due to severe postanoxic neurological damage in 23 of 28 deaths (82.1%). The remaining 5 patients died due to their underlying cardiac disease (P < .01). The variables associated with neurological damage were out-of hospital resuscitation, delay in beginning resuscitation maneuvers, arrival time > 5 minutes and unconsciousness on admission.

CONCLUSIONS

Although many patients survive following resuscitation from out-of-hospital sudden cardiac death, mortality remains high. Neurological impairment is the main cause of mortality. Prognosis is determined by the variables related to the underlying disease, the delay in onset of resuscitation maneuvers and postanoxia cerebral damage.

Dysrhythmia and electrocardiographic changes in diabetes mellitus: pathophysiology and impact on the incidence of sudden cardiac death

BACKGROUND

The incidence of sudden cardiac death (SCD) is increasing in diabetes mellitus. Susceptibility to dysrhythmias and the reliability of an electrocardiogram in diabetic hearts are debatable issues.

OBJECTIVES

To highlight the underlying mechanism of dysrhythmia and electrocardiographic changes in diabetic patients and the impact on the incidence of SCD.

METHODS

Most the pertinent articles (English and non-English) published in Medline, Scopus and EBSCO Host research databases have been reviewed.

RESULTS AND CONCLUSION

In the absence of systematic reviews, susceptibility to dysrhythmias and electrical instability in diabetic patients are underestimated. This susceptibility has been found to be enhanced, unchanged or reduced in different studies. To find a link between SCD and diabetes, the published studies provide controversial results; however, the majority of studies with a long-term follow-up support this link. The role of hyperglycemia, autonomic neuropathy and anti-diabetic agents as predisposing factors deserve more attention to fortify the clinical judgment and decrease the incidence of SCD.

Circadian rhythm of the autonomic nervous system in insulin resistant subjects with normoglycemia, impaired fasting glycemia, impaired glucose tolerance, type 2 diabetes mellitus

Background

In type 2 diabetes mellitus both insulin resistance and hyperglycemia are considered responsible for autonomic dysfunction. The relation between the autonomic activity, impaired fasting glycemia and impaired glucose tolerance is, however, unclear. The purpose of this study was to evaluate and compare the circadian autonomic activity expressed as heart rate variability (HRV) measured by 24-hours ECG recording in insulin resistant subjects (IR) with characteristics as follow: IR subjects with normal oral glucose tolerance test results, IR subjects with impaired fasting glucose, IR subjects with impaired glucose tolerance and subjects with type 2 diabetes mellitus.

Methods

Eighty Caucasian insulin resistant subjects (IR) and twenty five control subjects were recruited for the study. IR subjects were divided into four groups according to the outcoming results of oral glucose tests (OGTTs): IR subjects with normal glucose regulation (NGR), IR subjects with impaired fasting glycemia (IFG), IR subjects with impaired glucose tolerance (IGT) and subjects with type 2 diabetes mellitus (DM). Autonomic nervous activity was studied by 24-hours ECG recording. Heart rate variability analysis was performed in time and frequency domains: SDNN, RMS-SD, low frequency (LF) and high frequency (HF) were calculated.

Results

The total SDNN showed statistically significant reduction in all four groups with insulin resistant subjects (IR) when compared to the control group (p <0,001). During night LF normalized units (n.u.) were found to be higher in all four groups including IR subjects than in the control group (all p < 0,001) and subjects with normal glucose regulation (NGR), with impaired fasting glycemia (IFG) and with impaired glucose tolerance (IGT) were found to have higher LF n.u. than those in the type 2 diabetes mellitus group. The linear regression model demonstrated direct association between LF values and the homeostasis model assessment-index (HOMA-I), in the insulin resistant group (r = 0,715, p <0,0001).

Conclusion

The results of our study suggest that insulin resistance might cause global autonomic dysfunction which increases along with worsening glucose metabolic impairment. The analysis of sympathetic and parasympathetic components and the sympathovagal balance demonstrated an association between insulin resistance and sympathetic over-activity, especially during night. The results indicated that the sympathetic over-activity is directly correlated to the grade of insulin resistance calculated according to the HOMA-I. Since increased sympathetic activity is related to major cardiovascular accidents, early diagnosis of all insulin resistant patients should be contemplated.

Increased Prevalence of Third-Degree Atrioventricular Block in Patients With Type II Diabetes Mellitus

BACKGROUND

Diabetes mellitus (DM) is a major risk for cardiovascular disease and mortality. There is some evidence that third-degree atrioventricular (AV) block occurs more commonly in patients with DM. In this study, we evaluated any possible association between DM and third-degree AV block using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes in a very large inpatient database.

METHOD

We used patient treatment files containing discharge diagnoses using ICD-9 codes of inpatient treatment from all Veterans Health Administration hospitals. The cohort was stratified using the ICD-9-CM code for DM (n = 293,124), a control group with hypertension but no DM (n = 552,623), and the ICD-9 code for third-degree AV block (426.0) and smoking (305.1, V15.82). We performed multivariate analysis adjusting for coronary artery disease, congestive heart failure, smoking, and hyperlipidemia. Continuous and binary variables were analyzed using chi2 and Fisher exact tests.

RESULTS

Third-degree AV block diagnosis was present in 3,240 of DM patients (1.1%) vs 3,367 patients (0.6%) in the control group. Using multivariate analysis, DM remained strongly associated with third-degree AV block (odds ratio, 3.1; 95% confidential interval, 3.0 to 3.3; p < 0.0001).

CONCLUSION

Third-degree AV block occurs significantly more in patients with DM. This finding may, in part, explain the high cardiovascular mortality in DM patients.