Serum asymmetric dimethylarginine as a marker of coronary microcirculation in patients with non-insulin dependent diabetes mellitus: correlation with coronary flow reserve

Coronary microvascular function is independently associated with left ventricular filling pressure in patients with type 2 diabetes mellitus

BACKGROUND

Left ventricular (LV) diastolic dysfunction is known as an early marker of myocardial alterations in patients with diabetes. Because microvascular disease has been regarded as an important cause of heart failure or diastolic dysfunction in diabetic patients, we tested the hypothesis that coronary flow reserve (CFR), which reflects coronary microvascular function, is associated with LV diastolic dysfunction in patients with type 2 diabetes.

METHODS

We studied asymptomatic patients with type 2 diabetes but without overt heart failure. Transthoracic Doppler echocardiography was performed that included pulsed tissue Doppler of the mitral annulus and CFR of the left anterior descending artery (induced by adenosine 0.14 mg/kg/min). The ratio of mitral velocity to early diastolic velocity of the mitral annulus (E/e') was used as a surrogate marker of diastolic function. We also evaluated renal function, lipid profile, parameters of glycemic control and other clinical characteristics to determine their association with E/e'. Patients with LV ejection fraction <50%, atrial fibrillation, valvular disease, regional wall motion abnormality, renal failure (serum creatinine >2.0 mg/dl) or type 1 diabetes were excluded. Patients with a CFR <2.0 were also excluded based on the suspicion of significant coronary artery stenosis.

RESULTS

We included 67 asymptomatic patients with type 2 diabetes and 14 non-diabetic controls in the final study population. In univariate analysis, age, presence of hypertension, LV mass index, estimated glomerular filtration rate and CFR were significantly associated with E/e'. Multivariate analysis indicated that both LV mass index and CFR were independently associated with E/e'. In contrast, there were no significant associations between parameters of glycemic control and E/e'.

CONCLUSIONS

CFR was associated with LV filling pressure in patients with type 2 diabetes. This result suggests a possible link between coronary microvascular disease and LV diastolic function in these subjects.

Prognostic value of coronary flow reserve assessed by transthoracic Doppler echocardiography on long-term outcome in asymptomatic patients with type 2 diabetes without overt coronary artery disease

BACKGROUND

Cardiovascular risk stratification of asymptomatic diabetic patients is important and remains a difficult clinical problem. Our aim was to test the hypothesis that coronary flow reserve (CFR) assessed by noninvasive transthoracic Doppler echocardiography predicts prognosis in those patients.

METHODS

From February 2002 to January 2005, we evaluated 135 consecutive asymptomatic patients (74 male; mean age, 63 ± 9 years) with type 2 diabetes without a history of coronary artery disease. Adenosine triphosphate (0.14 mg/kg/min) stress Doppler echocardiography was performed to evaluate CFR of the left anterior descending artery. Patients with a CFR < 2.0 were also excluded based on the suspicion of significant coronary artery stenosis in the left anterior descending artery.

RESULTS

There were 111 patients (60 male; mean age, 64 ± 9 years) enrolled. During a median follow-up of 79 months, 20 events (5 deaths, 7 acute coronary syndromes, 8 coronary revascularizations) occurred. The optimal cut-off value of CFR to predict events was 2.5 (area under the receiver-operating characteristic curve = 0.65). Multivariate analysis showed that the independent prognostic indicators were male gender (p < 0.05) and a CFR < 2.5 (p < 0.01). Kaplan-Mayer analysis revealed that the event rate was significantly higher (log-lank, p < 0.01) in patients with CFR < 2.5 than in those with CFR ≥ 2.5.

CONCLUSIONS

CFR obtained by transthoracic Doppler echocardiography provides independent prognostic information in asymptomatic patients with type 2 diabetes without overt coronary artery disease. Patients with CFR < 2.5 had a worse long-term outcome.

Effect of angiotensin-converting enzyme inhibitor on serum asymmetric dimethylarginine and coronary circulation in patients with type 2 diabetes mellitus

Measurements of serum asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and coronary flow velocity reserve (CFVR) using transthoracic Doppler echocardiography were performed at baseline and after 4 weeks of temocapril therapy (2 mg/day) in 18 patients with type 2 diabetes. Although blood pressure, fasting blood sugar and lipid profiles remained unchanged, serum ADMA concentrations decreased significantly (0.51+/-0.08 to 0.46+/-0.07 micromol/l, p<0.01) and CFVR increased significantly (2.78+/-0.36 to 3.35+/-0.46, p<0.001) after the treatment. Moreover, a strong correlation was observed between the difference of ADMA and that of CFVR (r=-0.80, p<0.001). Temocapril reduced serum ADMA concentrations, improved CFVR beyond its blood pressure lowering effect. Our results suggest that decrease in ADMA by temocapril treatment is related to improvement of coronary circulation as determined by CFVR in patients with type 2 diabetes.