Cardiovascular remodelling in coronary artery disease and heart failure

Remodelling is a response of the myocardium and vasculature to a range of potentially noxious haemodynamic, metabolic, and inflammatory stimuli. Remodelling is initially functional, compensatory, and adaptive but, when sustained, progresses to structural changes that become self-perpetuating and pathogenic. Remodelling involves responses not only of the cardiomyocytes, endothelium, and vascular smooth muscle cells, but also of interstitial cells and matrix. In this Review we characterise the remodelling processes in atherosclerosis, vascular and myocardial ischaemia-reperfusion injury, and heart failure, and we draw attention to potential avenues for innovative therapeutic approaches, including conditioning and metabolic strategies.

Equivalence of indapamide SR and enalapril on microalbuminuria reduction in hypertensive patients with type 2 diabetes

OBJECTIVES

To test whether microalbuminuria in patients with type 2 diabetes and hypertension is primarily dependent on the severity of hypertension, and to compare the effectiveness of two antihypertensive drugs with opposite effects on the renin-angiotensin system [the diuretic, indapamide sustained release (SR), and an angiotensin-converting enzyme inhibitor, enalapril] in reducing microalbuminuria.

DESIGN

A multinational, multicentre, controlled, double-blind, double-dummy, randomized, two-parallel-groups study over 1 year.

METHODS

After a 4-week placebo run-in period, 570 patients (ages 60.0 +/- 9.9 years, 64% men) with type 2 diabetes, essential hypertension [systolic blood pressure (SBP) 140-180 mmHg, and diastolic blood pressure (DBP) < 110 mmHg], and persistent microalbuminuria (20-200 microg/min) were allocated randomly to groups to receive indapamide SR 1.5 mg (n = 284) or enalapril 10 mg (n = 286) once a day. Amlodipine, atenolol, or both were added, if necessary, to achieve the target blood pressure of 140/85 mmHg.

RESULTS

There was a significant reduction in the urinary albumin : creatinine ratio. Mean reductions were 35% [95% confidence interval (CI) 24 to 43] and 39% (95% CI 30 to 47%) in the indapamide SR and enalapril groups, respectively. Equivalence was demonstrated between the two groups [1.08 (95% CI 0.89 to 1.31%); P = 0.01]. The reductions in mean arterial pressure (MAP) were 16.6 +/- 9.0 mmHg for the indapamide SR group and 15.0 +/- 9.1 mmHg for the enalapril group (NS); the reduction in SBP was significantly greater (P = 0.0245 ) with indapamide SR. More than 50% of patients in each group required additional antihypertensive therapy, with no differences between groups. Both treatments were well tolerated.

CONCLUSIONS

Indapamide-SR-based therapy is equivalent to enalapril-based therapy in reducing microalbuminuria with effective blood pressure reduction in patients with hypertension and type 2 diabetes.

Effect of extracellular pH on function and metabolism of isolated perfused rat heart

The extracellular pH of the isolated perfused rat heart was varied from 6.9 to 8.0 usually by altering the bicarbonate content of the buffer. Isovolumic left ventricular contractility was measured by an intraventricular balloon. The peak systolic pressure was dependent on the coronary flow rate. At a constant flow rate the peak pressure and cardiac rate were unchanged at 7.4–8.0 but declined at about pH 7.1. The uptake and fate of pyruvate-1-C14 (6 mm) and palmitate-1-C14 (0.7 mm) were similar at pH 7.1–8.0. Compared with pH 7.4, oxidation rates of glucose-U-C14 (5 mm) and acetate-2-C14 (5 mm) were unchanged at pH 7.1, but were greater at pH 8.0. Other increases at pH 8.0 (glucose 5 mm) were in glucose uptake, lactate and pyruvate formation, and the percentage of the glucose uptake accounted for by the sum of C14O2, lactate, and pyruvate formed. It is concluded that in spite of decreased mechanical activity at pH 7.1, Krebs cycle activity is unaltered by pH changes from 7.1 to 8.0, whereas glycolysis and acetate oxidation increase above pH 7.4.

Predisposing factors and incidence of newly diagnosed atrial fibrillation in an urban African community: insights from the Heart of Soweto Study

BACKGROUND

Little is known about the incidence and clinical characteristics of newly diagnosed atrial fibrillation/flutter (AF) in urban Africans in epidemiological transition.

METHODS

This observational cohort study was carried out in the Chris Hani Baragwanath Hospital in Soweto South Africa. A clinical registry captured detailed clinical data on all de novo cases of AF presenting to the Cardiology Unit during the period 2006-2008.

RESULTS

Overall, 246 of 5328 cardiac cases (4.6%) presented with AF (estimated 5.6 cases/100 000 population/annum). Mean age was 59±18 years and the majority were of African descent (n=211, 86%) and/or female (n=150, 61%). Men were more than twice as likely to smoke (OR 2.88, 95% CI 1.92 to 4.04) than women, but women were twice as likely to be obese (OR 1.80, 95% CI 1.28 to 2.52) than men. Lone AF occurred in 22 (8.9%) cases, while concurrent valve disease and/or functional valvular abnormality occurred in 107 cases (44%). Overall, 171 cases (70%) presented with uncontrolled AF (ventricular rate >90 beats/min) with no sex-based differences. Common co-morbidities were any form of heart failure (56%) and rheumatic heart disease (21%). Women with AF were more likely to present with hypertensive heart failure (OR 2.37, 95% CI 1.24 to 4.54) but less likely to present with a dilated cardiomyopathy (OR 0.42, 95% CI 0.23 to 0.76) or coronary artery disease (OR 0.38, 95% CI 0.14 to 1.02) than men. Mean overall CHADS(2) score (in 195 non-rheumatic cases) was 1.51±0.91 and, despite a similar age profile, women had higher scores than men (1.73±0.94 vs 1.24±0.78; p<0.0001).

CONCLUSIONS

These unique data suggest that urban Africans in Soweto develop AF at a relatively young age. Conventional strategies used to manage and treat AF need to be carefully evaluated in this setting.

Free radicals trigger TNF?-induced cardioprotection

OBJECTIVE

Tumor Necrosis Factor alpha (TNF alpha) induces programmed cell death and contributes to cardiac ischemia/reperfusion injury. Paradoxically, we have recently demonstrated that low doses of TNF alpha can induce cardiac preconditioning (PC). We hypothesized that the production of free radicals participates in this cardioprotective program.

METHODS

Control isolated rat hearts underwent 30 min regional ischemia and 120 min of reperfusion. A second group of hearts received a low dose of TNF alpha (0.5 ng/ml) for 7 min followed by 10 min washout prior to I/R. In other groups, the antioxidant N-2-mercaptopropionyl glycine (MPG) (1 mM) was given for 15 min prior to I/R alone or during TNF alpha perfusion. Infarct size was determined at the end of the reperfusion period. Ventricular catalase and superoxide dismutase activities were assessed as an index of oxidative stress and free radical production was directly measured by the oxidation of 1-hydroxy-3-carboxy-pyrrolidine (CP-H) to paramagnetic 3-carboxy-proxyl (CP.) using electron spin resonance spectroscopy.

RESULTS

TNF alpha reduced the infarct/area at risk (I/AAR) ratio (7.2+/-1.7% vs. 36.5+/-1.7% for controls, p<0.05). MPG reduced the cardioprotective effect of TNF alpha (I/AAR ratio: 20.5+/-3.3%, p<0.05). TNF alpha-perfusion increased catalase activity in the ventricles (15.8+/-1.2 I.U./mg for controls vs. 19.9+/-1.1 I.U/mg for TNF alpha, p<0.05). Proof of formation of free radicals was increased CP formation in the coronary effluent during TNF alpha infusion (24.2+/-4.5 for TNF alpha vs. 11.9+/-1.5 arbitrary units for controls, p<0.05), with decreased CP after addition of MPG.

CONCLUSIONS

Our data provide firm evidence for a production and role of free radicals in TNF alpha-induced cardioprotection.

Coronary heart disease in marathon runners

Six highly trained marathon runners developed myocardial infarction. One of the two cases of clinically diagnosed myocardial infarction was fatal, and there were four cases of angiographically-proven infarction. Two athletes had significant arterial disease of two major coronary arteries, a third had stenosis of the anterior descending and the fourth of the right coronary artery. All these athletes had warning symptoms. Three of them completed marathon races despite symptoms, one athlete running more than 20 miles after the onset of exertional discomfort to complete the 56 mile Comrades Marathon. In spite of developing chest pain, another athlete who died had continued training for three weeks, including a 40 mile run. Two other athletes also continued to train with chest pain. We conclude that the marathon runners studied were not immune to coronary heart disease, nor to coronary atherosclerosis and that high levels of physical fitness did not guarantee the absence of significant cardiovascular disease. In addition, the relationship of exercise and myocardial infarction was complex because two athletes developed myocardial infarction during marathon running in the absence of complete coronary artery occlusion. We stress that marathon runners, like other sportsmen, should be warned of the serious significance of the development of exertional symptoms. Our conclusions do not reflect on the possible value of exercise in the prevention of coronary heart disease. Rather we refute exaggerated claims that marathon running provides complete immunity from coronary heart disease.

Positron emission tomographic evaluation of regulation of myocardial perfusion in physiological (elite athletes) and pathological (systemic hypertension) left ventricular hypertrophy

Myocardial perfusion (MP) may differ in physiologic and pathologic left ventricular hypertrophy (LVH). We compared MP in LVH in elite athletes and patients with hypertension with healthy, age-matched subjects. We included 12 rowers with LVH, 19 patients with hypertension with LVH, and 2 age-matched groups of healthy subjects (n = 11 and n = 12). The left ventricular mass index was determined echocardiographically. MP was measured by N-13 ammonia positron emission tomography. The maximal perfusion and perfusion reserve were studied using dipyridamole, and endothelial function was assessed by a cold pressor test. The degree of LVH was similar in athletes and those with hypertension. Compared with controls, athletes had 20% lower baseline MP (p <0.05), a similar response to the cold pressor test, and a higher perfusion reserve (31%, p <0.05). The patients with hypertension had a 25% higher baseline MP (p <0.05), a reduced increase during the cold pressor test (12% vs 25% in controls, p <0.05), and a reduced perfusion reserve (27% lower, p <0.001). The peak global perfusion (MP x left ventricular mass index) was 62% higher in athletes (p <0.05) than in controls, but the peak global perfusion in patients with hypertension did not differ from that of controls. In conclusion, physiologic LVH in athletes is suited for a high peak workload at the cost of only a small increase in basal myocardial oxygen consumption. In contrast, LVH in the presence of hypertension is a good adaptation to the increased baseline workload with maintained maximal cardiac performance. Endothelial dysfunction may contribute to the reduced perfusion reserve seen in hypertensive LVH.

Efficacy of indapamide SR compared with enalapril in elderly hypertensive patients with type 2 diabetes

BACKGROUND

Blood pressure control is the main influential variable in reducing microalbuminuria in patients with type 2 diabetes. In this subanalysis of the Natrilix SR versus Enalapril Study in hypertensive Type 2 diabetics with micrOalbuminuRia (NESTOR) study, we have compared the effectiveness of indapamide sustained release (SR) and enalapril in reducing blood pressure and microalbuminuria in patients > or =65 years of age.

METHODS

Of the 570 hypertensive patients with type 2 diabetes and persistent microalbuminuria in the NESTOR study, 187 (33%) individuals > or =65 years of age were included in this analysis. Of these, 95 patients received indapamide SR 1.5 mg and 92 patients received enalapril 10 mg, taken once daily in both cases. Adjunctive amlodipine and/or atenolol was added if required.

RESULTS

The urinary albumin-to-creatinine ratio decreased by 46% in the indapamide SR group and 47% in the enalapril group. Noninferiority of indapamide SR over enalapril was demonstrated (P = .0236; 35% limit of noninferiority) with a ratio of 0.95 (95% CI: 0.68, 1.34). Mean arterial pressure decreased by 18 mm Hg and 15 mm Hg in the indapamide SR and the enalapril groups, respectively (P = .1136). The effects of both treatments seen in these elderly patients were similar to those observed in the main population, although the extent of the reduction in microalbuminuria was slightly higher. Both treatments were well tolerated, and no difference between groups was observed regarding glucose or lipid profiles.

CONCLUSION

Indapamide SR is not less effective than enalapril in reducing microalbuminuria and blood pressure in patients aged >65 years of age with type 2 diabetes and hypertension.

TNFα-induced cytoprotection requires the production of free radicals within mitochondria in C2C12 myotubes

We previously reported that tumour necrosis factor alpha (TNFalpha) can mimic classic ischemic preconditioning (IPC) in both cells and heart. However, the signalling pathways involved remain incompletely understood. One potential protective pathway could be TNFalpha-induced reactive oxygen species (ROS). We hypothesized that TNFalpha cytoprotection occurs through the generation of ROS which originate within the mitochondria. C(2)C(12) myotubes were preconditioned with either a short period of hypoxia (IPC) or a low concentration of TNFalpha (0.5 ng/ml) prior to a simulated ischemic insult. ROS generation was evaluated on cells stained with dichlorofluorescin diacetate (DCFH-DA) by flow cytometry. The source of TNFalpha-induced ROS was examined with Mitotracker Red CM-H(2)XRos. The bioenergetics of the mitochondria were evaluated by investigation of the respiratory parameters and the inner mitochondrial membrane potential. Pretreatment with TNFalpha improved cell viability compared with the simulated ischemic control (TNFalpha: 75 +/- 1% versus 34 +/- 1% for the control: p<0.001). The ROS scavenger, N-2-mercaptopropionyl-glycine (MPG), reduced the viability of TNFalpha-stimulated cells to 15 +/- 1% (p<0.001 versus TNFalpha). Similar results were obtained with IPC. TNFalpha stimulation increased ROS production mainly in the mitochondria, and this increase was abolished in the presence of MPG. Addition of TNFalpha to the cells increased State 2 respiration and modestly depolarised the membrane potential prior to the ischemic insult. In conclusion, TNFalpha-induced ROS generation can occur within the mitochondria, resulting in temporal mitochondrial perturbations which may initiate the cytoprotective effect of TNFalpha.

Age, genetic characteristics and number of cycles are critical factors to consider for successful protection of the murine heart with postconditioning

Postconditioning (PostC) is a recently discovered phenomenon whereby brief repetitive cycles of ischaemia with intermittent reperfusion following prolonged ischaemia elicit cardioprotection. This study investigated whether the age, genetic characteristics or number of repetitive cycles influenced the protective effect of PostC in mice. C57BL/6 floxed or non-floxed STAT-3 mice aged between 14-16 weeks (young) or 18-20 weeks (older) were perfused on a Langendorff apparatus and subjected to 35 min global ischaemia and 45 min reperfusion. PostC was elicited by either 3 (PostC-3) or 6 cycles (PostC-6) of 10 s ischaemia and 10 s reperfusion. PostC-3 and PostC-6 in both young and older non-floxed mice reduced the myocardial infarct size. In contrast, only PostC-3 reduced myocardial infarct size in young floxed mice. Neither PostC-3 nor PostC-6 reduced the infarct in older floxed mice. Our data reveal that genetic characteristics, a minute difference in age or the number of postconditioning cycles are critical factors to be considered for the successful effect of ischaemic postconditioning in a murine model. Moreover, these factors should be taken into consideration for future experimental research or clinical applications of this protective phenomenon.

Left Ventricular Systolic Dysfunction in Asymptomatic Black Hypertensive Subjects

BACKGROUND

Hypertension has been established as one of the commonest causes of heart failure especially in sub-Saharan Africa. We have previously observed a high prevalence of left ventricular (LV) systolic dysfunction in hypertensive heart failure patients in Nigeria despite a low prevalence of ischemic heart disease. The present study was, therefore, undertaken to assess the prevalence of asymptomatic LV systolic dysfunction in hypertensive black African subjects with no history of heart failure.

METHODS

One thousand nine hundred forty-seven hypertensive subjects without heart failure presenting to the Cardiology Unit, Department of Medicine, University of Abuja Teaching Hospital, Nigeria, from April 2006 to August 2013 had clinical and echocardiographic evaluation.

RESULTS

Nine hundred fifty-three (48.9%) were males and 994 (51.1%) were females. One thousand eight hundred seventeen (93.3%) had normal LV systolic function (LV ejection fraction (LVEF) ≥ 54%), 68 (3.5%) had mild LV systolic dysfunction (LVEF 45-54%), 43 (2.3%) had moderate LV systolic dysfunction (LVEF 30-44%), and 16 (0.9%) had severe LV systolic dysfunction (LVEF < 30%). Male subjects had worse LV systolic function compared to women (mean LVEF 73.2% vs. 75.6%, P value < 0.0001) and diabetic subjects had worse LV systolic function compared to nondiabetic subjects (LVEF 72.3% vs. 75.7%, P = 0.02). In multivariate regression analysis, lower LVEF as a continuous variable was associated with older age, male sex, diabetes mellitus, LV mass indexed for body surface area, diastolic blood pressure, posterior wall thickness in diastole, left atrial diameter, and LV internal diameter in diastole.

CONCLUSIONS

In a cohort of asymptomatic Black hypertensive subjects, 6.7% had LV systolic dysfunction, which was associated with male gender, diabetes mellitus, and larger LV mass.