Impaired left ventricular diastolic filling occurs in diabetic patients without atherosclerotic coronary artery disease

Diabetes and incident heart failure in hypertensive and normotensive participants of the Strong Heart Study

OBJECTIVES

Type 2 diabetes is accepted as a cause of heart failure, but direct cause-effect evidence independent of incident myocardial infarction (MI), hypertension and other coexisting risk factors is less well studied. We tested the hypothesis that diabetes predisposes to heart failure independently of hypertension and intercurrent MI.

METHODS

We evaluated 12-year incident heart failure in 2740 participants (1781 women) without prevalent cardiovascular or severe kidney disease, at the time of the first exam of the Strong Heart Study cohort. Intercurrent MI was censored as a competing risk event.

RESULTS

Diabetes was present in 1206 individuals (44%), and impaired fasting glucose (IFG) in 391 (14%). Diabetic participants more frequently had hypertension and/or central obesity (both P < 0.0001). Incident heart failure was ascertained in 64 participants with normal fasting glucose (NFG; 6%), 26 (7%) with IFG and 201 with diabetes (17%, hazard ratio = 4.04 vs. NFG, P < 0.0001). In Cox analysis adjusting for age, sex, obesity, central fat distribution, hypertension, antihypertensive medications, prevalent atrial fibrillation, glomerular filtration rate, urinary albumin/creatinine ratio, plasma cholesterol, Hb1Ac, smoking habit, alcohol use, educational level and physical activity, diabetes was associated with a two-fold greater risk of incident heart failure than NFG (hazard ratio = 2.45, P < 0.0001). Diabetes maintained 1.5-fold greater risk of heart failure than NFG (P < 0.03) even when intercurrent MI (n = 221) was censored as a competing risk event, similar to the adjusted hazard ratio for heart failure in hypertension.

CONCLUSION

Type 2 diabetes is a potent, independent risk factor for heart failure. Risk of heart failure in diabetic patients cannot be fully explained by incident MI and coexisting cardiovascular risk factors. Mechanisms directly related to diabetes and impairing cardiac function should be studied and identified.

Diastolic dysfunction: a link between hypertension and heart failure

Diastolic heart failure is characterized by the symptoms and signs of heart failure, a preserved ejection fraction and abnormal left ventricular (LV) diastolic function caused by a decreased LV compliance and relaxation. The signs and symptoms of diastolic heart failure are indistinguishable from those of heart failure related to systolic dysfunction; therefore, the diagnosis of diastolic heart failure is often one of exclusion. The majority of patients with heart failure and preserved ejection fraction have a history of hypertension. Hypertension induces a compensatory thickening of the ventricular wall in an attempt to normalize wall stress, which results in LV concentric hypertrophy, which in turn decreases LV compliance and LV diastolic filling. There is an abnormal accumulation of fibrillar collagen accompanying the hypertension-induced LV hypertrophy, which is also associated with decreased compliance and LV diastolic dysfunction. There are no specific guidelines for treating diastolic heart failure, but pharmacological treatment should be directed at normalizing blood pressure, promoting regression of LV hypertrophy, preventing tachycardia and treating symptoms of congestion. Preventive strategies directed toward an early and aggressive blood pressure control are likely to offer the greatest promise for reducing the incidence of diastolic heart failure.

Left ventricular diastolic function in normotensive subjects 2 months after acute myocardial infarction is related to glucose intolerance

BACKGROUND

Both glucose intolerance and myocardial infarction are independently associated with impaired left ventricular (LV) function. This study was carried out to relate LV diastolic function in normotensive subjects 2 months after acute myocardial infarction (AMI) to glucose tolerance status.

METHODS

Left ventricular ejection fraction (LVEF), LV mass index, peak velocity of the early phase/atrial contraction wave, deceleration time of E wave, and isovolumic relaxation time were measured during echocardiograph/Doppler cardiography in 200 normotensive patients 2 months after AMI. Twenty-nine patients were known to be diabetic on admission with AMI. Glucose tolerance test was carried out in the 171 patients who are not known to be diabetic.

RESULTS

Independent of LVEF, restrictive LV filling (peak velocity of the early phase/atrial contraction wave > 1 but < 2 associated with deceleration time of E wave < or = 140 milliseconds) was found in 72% of the known-diabetic patients, 70% of the 20 preclinical diabetic patients, 23% of the 35 patients with impaired glucose tolerance, 13% of the 15 patients with stress hyperglycemia, and 7% of the euglycemic patients (P < .01). In the rest of these patients, LV filling was nonrestrictive. No significant difference was observed in LVEF and LV mass index between patient groups.

CONCLUSION

Independent of LVEF, the pattern of abnormal LV filling in normotensive subjects 2 months after AMI is a function of the severity of glucose intolerance, restrictive in the majority of the diabetic patients and nonrestrictive in the majority of the euglycemic patients, impaired glucose tolerance, and stress hyperglycemia. After AMI, abnormal LV filling occurs even in the absence of detectable systolic dysfunction or left ventricular hypertrophy.

Superoxide-NO interaction decreases flow- and agonist-induced dilations of coronary arterioles in Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2-DM) markedly increases the incidence of ischemic heart disease (IHD) and, consequently, mortality. However, the underlying mechanisms leading to IHD in T2-DM are not completely understood. We hypothesized that in T2-DM the regulation of coronary microvascular resistance by local mechanisms is altered. Thus, in coronary arterioles (diameter: approximately 80 microm) isolated from male mice with T2-DM (C57BL/KsJ-db/db) and control littermates, responses to changes in intraluminal pressure, flow, and agonists with known mechanisms of action were studied. Increases in pressure (from 20 to 120 mmHg) resulted in similar myogenic responses of coronary arterioles of control and db/db mice, whereas dilations in response to cumulative concentrations of ACh and the nitric oxide (NO) donor NONOate were significantly decreased compared with those of control vessels. On the other hand, responses to adenosine were not different between vessels of control and db/db mice. Increases in flow (0-20 microl/min) resulted in dilations of control vessels (maximum: 38 +/- 4%) that were inhibited by the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME). In contrast, arterioles of db/db mice exhibited greatly reduced dilations to flow (maximum: 4 +/- 6%) that were unaffected by L-NAME. In carotid arteries of db/db mice, superoxide dismutase (SOD)-sensitive, enhanced superoxide production was detected by dihydroethydine staining and lucigenin enhanced chemiluminescence. Correspondingly, intraluminal administration of SOD significantly augmented flow-, ACh-, and NONOate-induced dilations of diabetic arterioles, and then flow- and ACh-induced responses could be inhibited by L-NAME. Collectively, these findings suggest that in T2-DM, due to an enhanced superoxide production, NO mediation of agonist- and flow-induced dilations of coronary arterioles is reduced. This alteration in the regulation of coronary microvascular resistance may contribute to the development of IHD in T2-DM.

Echocardiographic evaluation of left and right ventricular function in mild hypertension

Thirty-one cases of untreated 'mild hypertension' and equal number of age and sex matched controls with 'normal' blood pressure were evaluated by echocardiography. Patients with mild hypertension had significantly increased left ventricular mass index, concentric remodeling, and diastolic dysfunction. Thickness of right ventricular anterior wall, flow velocities across tricuspid and pulmonary valves were also significantly higher in hypertensives. Pulmonary flow acceleration time was significantly less in hypertensives. On multiple regression analysis, mitral valve 'A' wave velocity alone correlated with systolic blood pressure. Other echocardiographic variables did not have any relation with blood pressure readings. Height, weight, body surface area and body mass index could also explain only around 50% of variability in echocardiographic parameters. Cardiac structure and functions in hypertensives are affected by factors other than blood pressure reading, body surface area or body mass index. Routine echocardiography can be useful in identifying those patients of mild hypertension who have disproportionate increase in left ventricular mass or disproportionate impairment of diastolic functions.