Coronary Flow Reserve and Myocardial Performance Index in Newly Diagnosed Diabetic Patients

Prognostic value of myocardial performance index in individuals with type 1 and type 2 diabetes: Thousand&1 and Thousand&2 studies

AIMS

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in type 1 (T1D) and type 2 diabetes (T2D). Despite diabetes affects the myocardium, risk prediction models do not include myocardial function parameters. Myocardial performance index (MPI) reflects left ventricular function. The prognostic value of MPI has not been evaluated in large-scale diabetes populations.

METHODS AND RESULTS

We evaluated two prospective cohort studies: Thousand&1 (1093 individuals with T1D) and Thousand&2 (1030 individuals with T2D). Clinical data, including echocardiography, were collected at baseline. We collected follow-up data from national registries. We defined major adverse cardiovascular events (MACE) as incident events of hospital admission for acute coronary syndrome, heart failure, stroke, or all-cause mortality. For included individuals (56% male, 54 ± 15 years, MPI 0.51 ± 0.1, 63% T1D), follow-up was 100% after median of 5.3 years (range: 4.8-6.3). MPI was associated with MACE (HR 1.2, 95%CI 1.0-1.3, P = 0.012, per 0.10-unit increase) and heart failure (HR 1.3, 95%CI 1.1-1.6, P = 0.005, per 0.10-unit increase) after adjusting for clinical and echocardiographic variables. MPI predicted MACE and heart failure better in T1D than T2D (P = 0.031 for interaction). MPI added discriminatory power to the Steno T1 Risk Engine, based on clinical characteristics, in predicting MACE [area under the curve (AUC) from 0.77 to 0.79, P = 0.030] and heart failure (AUC from 0.77 to 0.83, P = 0.009) in T1D.

CONCLUSION

MPI is independently associated with MACE and heart failure in T1D but not T2D and improves prediction in T1D. Echocardiographic assessment in T1D may enhance risk prediction.

Coronary microvascular dysfunction is associated with cardiac time intervals in women with angina and no obstructive coronary artery disease: An iPOWER substudy

BACKGROUND

Coronary microvascular dysfunction (CMD) may cause angina in the absence of obstructive coronary artery disease (CAD) and increases the risk of future adverse cardiovascular events. Transthoracic Doppler echocardiography (TTDE) with pharmacological stress can assess coronary flow velocity reserve (CFVR), a measure of coronary microvascular function. However, simpler methods would be preferable for diagnosing CMD. Therefore, we examined the relationship between CFVR and cardiac time intervals measured by TTDE in a cohort of women with angina and no obstructive CAD.

METHODS

In a prospective cohort study, we included 389 women with angina, left ventricular ejection fraction > 45%, and no obstructive CAD. CMD was defined as CFVR < 2.0. The study population was divided into three groups according to cutoff values of CFVR < 2, 2 ≤ CFVR ≤ 2.5, and CFVR > 2.5. Isovolumic contraction time (IVCT), ejection time (ET), and isovolumic relaxation time (IVRT) were measured by tissue Doppler M-mode, and the myocardial performance index (MPI = (IVCT + IVRT)/ET) was calculated.

RESULTS

Coronary microvascular dysfunction was associated with increasing age, hypertension, higher resting heart rate, and lower diastolic blood pressure. Moreover, CMD was associated with higher E/e' ratio (P = 0.002) and longer IVCT (P < 0.001), higher MPI (P < 0.001) and shorter ET (P = 0.002), but not with IVRT or conventional measures of left ventricular geometry, mass, and function. In multivariable analysis, longer IVCT (P < 0.001) and higher MPI (P = 0.002) remained associated with CMD.

CONCLUSION

In women with angina and no obstructive CAD, CMD is associated with longer IVCT and higher MPI indicating a link between CMD and subtle alternations of systolic and combined measures of cardiac time intervals.

Diabetic cardiomyopathy: prevalence, determinants and potential treatments

The prevalence of type 2 diabetes (T2D) has reached a pandemic scale. These patients are at a substantially elevated risk of developing cardiovascular disease, with heart failure (HF) being a leading cause of morbidity and mortality. Even in the absence of traditional risk factors, diabetes still confers up to a twofold increased risk of developing HF. This has led to identifying diabetes as an independent risk factor for HF and recognition of the distinct clinical entity, diabetic cardiomyopathy. Despite a wealth of research interest, the prevalence and determinants of diabetic cardiomyopathy remain uncertain. This limited understanding of the pathophysiology of diabetic heart disease has also hindered development of effective treatments. Tight blood-glucose and blood-pressure control have not convincingly been shown to reduce macrovascular outcomes in T2D. There is, however, emerging evidence that T2D is reversible and that the metabolic abnormalities can be reversed with weight loss. Increased aerobic exercise capacity is associated with significantly lower cardiovascular and overall mortality in diabetes. Whether such lifestyle modifications as weight loss and exercise may ameliorate the structural and functional derangements of the diabetic heart has yet to be established. In this review, the link between T2D and myocardial dysfunction is explored. Insights into the structural and functional perturbations that typify the diabetic heart are first described. This is followed by an examination of the pathophysiological mechanisms that contribute to the development of cardiovascular disease in T2D. Lastly, the current and emerging therapeutic strategies to prevent or ameliorate cardiac dysfunction in T2D are evaluated.

RV diastolic dysfunction: time to re-evaluate its importance in heart failure

Right ventricular (RV) diastolic dysfunction was first reported as an indicator for the assessment of ventricular dysfunction in heart failure a little over two decades ago. However, the underlying mechanisms and precise role of RV diastolic dysfunction in heart failure remain poorly described. Complexities in the structure and function of the RV make the detailed assessment of the contractile performance challenging when compared to its left ventricular (LV) counterpart. LV dysfunction is known to directly affect patient outcome in heart failure. As such, the focus has therefore been on LV function. Nevertheless, a strategy for the diagnosis and assessment of RV diastolic dysfunction has not been established. Here, we review the different causal mechanisms underlying RV diastolic dysfunction, summarising the current assessment techniques used in a clinical environment. Finally, we explore the role of load-independent indices of RV contractility, derived from the conductance technique, to fully interrogate the RV and expand our knowledge and understanding of RV diastolic dysfunction. Accurate assessment of RV contractility may yield further important prognostic information that will benefit patients with diastolic heart failure.

Noninvasive study of coronary microcirculation response to a cold pressor test

BACKGROUND

The aims of this study were to noninvasively (i) assess the coronary microcirculation changes in response to a cold pressor test (CPT) in control subjects, nondiabetic obese patients and patients with type 2 diabetes and (ii) investigate the response of the coronary microcirculation in patients with diabetes according to the presence or the absence of silent myocardial ischaemia (SMI), asymptomatic coronary stenosis (CS) and left ventricle hypertrophy (LVH).

METHODS

The mean left anterior descending coronary flow velocity (mCFV) was measured using transthoracic Doppler before and after a CPT in 16 control subjects, 11 obese and 66 asymptomatic diabetic patients with a high cardiovascular risk. Patients with diabetes were screened for SMI using stress myocardial scintigraphy and/or echocardiography. A coronary angiography was performed in those with SMI.

RESULTS

At baseline, pressure-rate product (PRP) was correlated with mCFV (r = 0.23; P < 0.05) and left ventricle mass (r = 0.26; P < 0.05) in the whole population. Changes in PRP and mCFV during CPT were correlated with controls (r = 0.58, P < 0.05), obese (r = 0.75, P < 0.01) and diabetic patients without CS (r = 0.56, P < 0.0001) or without LVH (r = 0.63, P < 0.05) but not in diabetic patients with CS or with LVH. In patients with diabetes, SMI was associated with mCFV changes, independent of other parameters (P < 0.05).

CONCLUSION

Transthoracic coronary Doppler allows noninvasive study of changes in the coronary microcirculation during CPT. In asymptomatic patients with type 2 diabetes, this method showed that SMI was associated with mCFV changes during CPT and the presence of CS or LVH was associated with a mismatch between coronary microcirculation and myocardial oxygen demand.

The association between aortic distensibility and coronary flow reserve in newly diagnosed diabetic patients

INTRODUCTION

Aortic distensibility (AD) is an important parameter affecting coronary hemodynamics. Coronary flow velocity reserve (CFVR) is a reliable marker of coronary endothelial function in diabetic patients. The aim of this study was to investigate the association between AD and CFVR in newly diagnosed diabetic patients.

METHOD

We studied 77 patients with newly diagnosed diabetes mellitus (DM) and 30 age- and sex-matched healthy control subjects. CFVR was calculated as the hyperemic to resting coronary diastolic velocities ratio by using transthoracic echocardiography. Pulse pressure (PP) and AD were calculated.

RESULTS

Fasting blood glucose, HbA1c and PP were significantly higher in patients with diabetes (P < 0.001, P < 0.001 and P = 0.009, respectively). Other clinical and demographical characteristics, laboratory findings and echocardiographic findings were similar in both groups (P > 0.05, for all). The measurement of CFVR and AD in patients with diabetes were significantly lower compared with the controls (P < 0.001 and P = 0.001, respectively). CFVR was significantly negatively correlated with age, body mass index, HbA1c, systolic blood pressure, and PP, while significantly positively correlated with AD (P < 0.05, for all). Multivariate regression analysis showed that only AD (β = 0.485, P < 0.0001) and HbA1c (β = -0.362, P < 0.0001) were independently associated with CFVR. The cutoff value of AD obtained by the receiver operator characteristic (ROC) curve analysis was 2.44 for the prediction of impaired CFVR.

CONCLUSION

Aortic distensibility and HbA1c were independently associated with CFVR. The decrease in AD may be used as a marker of impaired coronary microcirculation in asymptomatic diabetic patients.