Effects of long-term treatment with carvedilol on myocardial blood flow in idiopathic dilated cardiomyopathy

Comparative Efficacy of Different Drugs for the Treatment of Dilated Cardiomyopathy: A Systematic Review and Network Meta-analysis

BACKGROUND AND OBJECTIVE

At present, the therapies of dilated cardiomyopathy concentrated on the symptoms of heart failure and related complications. The study is to evaluate the clinical efficacy of a combination of various conventional and adjuvant drugs in treating dilated cardiomyopathy via network meta-analysis.

METHODS

The study was reported according to the PRISMA 2020 statement. From inception through 27 June 2022, the PubMed, Embase, Cochrane library, and Web of Science databases were searched for randomized controlled trials on medicines for treating dilated cardiomyopathy. The quality of the included studies was evaluated according to the Cochrane risk of bias assessment. R4.1.3 and Revman5.3 software were used for analysis.

RESULTS

There were 52 randomized controlled trials in this study, with a total of 25 medications and a sample size of 3048 cases. The network meta-analysis found that carvedilol, verapamil, and trimetazidine were the top three medicines for improving left ventricular ejection fraction (LVEF). Ivabradine, bucindolol, and verapamil were the top 3 drugs for improving left ventricular end-diastolic dimension (LVEDD). Ivabradine, L-thyroxine, and atorvastatin were the top 3 drugs for improving left ventricular end-systolic dimension (LVESD). Trimetazidine, pentoxifylline, and bucindolol were the top 3 drugs for improving the New York Heart Association classification (NYHA) cardiac function score. Ivabradine, carvedilol, and bucindolol were the top 3 drugs for reducing heart rate (HR).

CONCLUSION

A combination of different medications and conventional therapy may increase the clinical effectiveness of treating dilated cardiomyopathy. Beta-blockers, especially carvedilol, can improve ventricular remodeling, cardiac function, and clinical efficacy in patients with dilated cardiomyopathy (DCM). Hence, they can be used if patients tolerate them. If LVEF and HR do not meet the standard, ivabradine can also be used in combination with other treatments. However, since the quality and number of studies in our research were limited, large sample size, multi-center, and high-quality randomized controlled trials are required to corroborate our findings.

Effect of Beta Blockers on the Hemodynamics and Thrombotic Risk of Coronary Artery Aneurysms in Kawasaki Disease

This study aims to simulate beta blockers' (BB) effects on coronary artery aneurysms' (CAA) hemodynamics and thrombotic risk in Kawasaki disease (KD). BB are recommended in cases of large aneurysms due to their anti-ischemic effect. Coronary blood flow (CBF) was simulated in KD patient-specific CAA models using computational fluid dynamics. Hemodynamic indices that correlate with thrombotic risk were calculated following two possible responses to BB: (1) preserved coronary flow (third BB generation) and (2) reduction in coronary flow (first and second BB generations) at reduced heart rate. Following CBF reduction scenario, mean TAWSS and HOLMES significantly decreased compared to normal conditions, leading to a potential increase in thrombotic risk. Preserved CBF at lower heart rates, mimicking the response to vasodilating BBs, does not significantly affect local CAA hemodynamics compared with baseline, while achieving the desired anti-ischemic effects. Different BB generations lead to different hemodynamic responses in CAA.

Coronary Microvascular Dysfunction: What Clinicians and Investigators Should Know

PURPOSE OF REVIEW

Abnormal structure and function of the coronary microvasculature have been implicated in the pathophysiology of multiple cardiovascular disease processes. This article reviews recent research progress related to coronary microvascular dysfunction (CMD) and salient clinical takeaways.

RECENT FINDINGS

CMD is prevalent in patients with signs and symptoms of ischemia and no obstructive epicardial coronary artery disease (INOCA), particularly in women. CMD is associated with adverse outcomes, including most frequently the development of heart failure with preserved ejection fraction. It is also associated with adverse outcomes in patient populations including hypertrophic cardiomyopathy, dilated cardiomyopathy, and acute coronary syndromes. In patients with INOCA, stratified medical therapy guided by invasive coronary function testing to define the subtype of CMD leads to improved symptoms. There are invasive and non-invasive methodologies to diagnose CMD that provide prognostic information and mechanistic information to direct treatment. Available treatments improve symptoms and myocardial blood flow; ongoing investigations aim to develop therapy to improve adverse outcomes related to CMD.

Updates on Pharmacologic Management of Microvascular Angina

Microvascular angina (MVA), historically called cardiac syndrome X, refers to angina with nonobstructive coronary artery disease. This female-predominant cardiovascular disorder adds considerable health-related costs due to repeated diagnostic angiography and frequent hospital admissions. Despite the high prevalence of this diagnosis in patients undergoing coronary angiography, it is still a therapeutic challenge for cardiologists. Unlike obstructive coronary artery disease, with multiple evidence-based therapies and management guidelines, little is known regarding the management of MVA. During the last decade, many therapeutic interventions have been suggested for the treatment of MVA. However, there is a lack of summarization tab and update of current knowledge about pharmacologic management of MVA, mostly due to unclear pathophysiology. In this article, we have reviewed the underlying mechanisms of MVA and the outcomes of various medications in patients with this disease. Contrary to vasospastic angina in which normal angiogram is observed as well, nitrates are not effective in the treatment of MVA. Beta-blockers and calcium channel blockers have the strongest evidence of improving the symptoms. Moreover, the use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, statins, estrogen, and novel antianginal drugs has had promising outcomes. Investigations are still ongoing for vitamin D, omega-3, incretins, and n-acetyl cysteine, which have resulted in beneficial initial outcomes. We believe that the employment of the available results and results of the future large-scale trials into cardiac care guidelines would help reduce the global cost of cardiac care tremendously.

Treatment strategies in coronary microvascular dysfunction: A systematic review of interventional studies

CMD has been associated with a wide spectrum of diseases and conditions, and it has proven to be a strong prognostic marker of morbidity and mortality. Despite increased attention, guideline-based treatment recommendations are lacking. We performed a systematic review of pharmacological and nonpharmacological interventions to improve coronary perfusion, assessed by IC Doppler, TTDE, PET, CMRI, transthoracic contrast perfusion echocardiography, and dilution techniques. No restrictions were made regarding the study design (randomized, placebo-controlled/randomized with active comparators/nonrandomized with or without a control group), the cardiac condition studied, or the coronary microvascular function at baseline. An electronic database search yielded 4485 records of which 80 studies met our inclusion criteria. Included studies were sorted according to intervention and study design. Studies were small and heterogeneous in methodology, and only few were placebo-controlled. Although some treatments looked promising, we found that no specific treatment was sufficiently well documented to be recommended in any patient groups. There is a need for larger well-designed clinical trials, and we suggest that future studies stratify study populations according to pathogenic mechanisms, thereby investigating whether an individualized treatment approach would be more successful.

Clinical efficacy of carvedilol treatment for dilated cardiomyopathy: A meta-analysis of randomized controlled trials

BACKGROUND

Clinical trials examining the therapeutic benefit of carvedilol on patients with dilated cardiomyopathy have reported inconsistent results. The aim of this study was to evaluate the clinical efficacy of carvedilol on patients with dilated cardiomyopathy.

METHODS

PubMed, Embase, Cochrane Library, web of science, China National Knowledge Infrastructure (CNKI), Wanfang, and Chinese Scientific and Technological Journal (VIP) databases were searched for randomized controlled trials (RCTs) before March 2018. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to evaluate the effects of carvedilol on patients with dilated cardiomyopathy.

RESULTS

Twenty one studies including 1146 participants were included. There were significant improvements on heart rate (HR) (WMD = -14.18, 95% CI: -17.72 to -10.63, P < .001), LVEF (WMD = 7.28, 95% CI: 6.53-8.03, P < .001), SBP (WMD = -10.74, 95% CI: -12.78 to -8.70, P < .001), DBP (WMD = -4.61, 95% CI: -7.32 to -1.90, P = .001), LVEDD (WMD = -2.76, 95% CI: -4.89 to -0.62, P = .011), LVESD (WMD = -3.63, 95% CI: -6.55 to -0.71, P = .015), LVEDV (WMD = -9.30, 95% CI: -11.89 to -6.71, P < .001), LVESV (WMD = -12.28, 95% CI: -14.86 to -9.70, P < .001) under carvedilol treatment compared with control.

CONCLUSION

This meta-analysis demonstrates that carvedilol significantly improves cardiac function on patients with dilated cardiomyopathy. Further large scale, high-quality and multicenter RCTs are still required to confirm the impacts of carvedilol on patients with dilated cardiomyopathy.

Clinical use of quantitative cardiac perfusion PET: rationale, modalities and possible indications. Position paper of the Cardiovascular Committee of the European Association of Nuclear Medicine (EANM)

Until recently, PET was regarded as a luxurious way of performing myocardial perfusion scintigraphy, with excellent image quality and diagnostic capabilities that hardly justified the additional cost and procedural effort. Quantitative perfusion PET was considered a major improvement over standard qualitative imaging, because it allows the measurement of parameters not otherwise available, but for many years its use was confined to academic and research settings. In recent years, however, several factors have contributed to the renewal of interest in quantitative perfusion PET, which has become a much more readily accessible technique due to progress in hardware and the availability of dedicated and user-friendly platforms and programs. In spite of this evolution and of the growing evidence that quantitative perfusion PET can play a role in the clinical setting, there are not yet clear indications for its clinical use. Therefore, the Cardiovascular Committee of the European Association of Nuclear Medicine, starting from the experience of its members, decided to examine the current literature on quantitative perfusion PET to (1) evaluate the rationale for its clinical use, (2) identify the main methodological requirements, (3) identify the remaining technical difficulties, (4) define the most reliable interpretation criteria, and finally (5) tentatively delineate currently acceptable and possibly appropriate clinical indications. The present position paper must be considered as a starting point aiming to promote a wider use of quantitative perfusion PET and to encourage the conception and execution of the studies needed to definitely establish its role in clinical practice.

Characterization of coronary flow reserve and left ventricular remodeling in a mouse model of chronic aortic regurgitation with carvedilol intervention

OBJECTIVES

We hypothesized that left ventricular (LV) remodeling might be exaggerated by an impaired coronary flow reserve in mice with chronic severe aortic regurgitation, and carvedilol, a β-adrenoceptor blocker, could regress the course.

METHODS

Severe aortic regurgitation was induced by retrograde puncture of the aortic valve leaflets under sonographic guidance in 12-week-old male C57BL/6J mice. Four weeks after regurgitation, the mice were treated with carvedilol (30 mg/kg/d) or not treated (control). Before and 4 weeks after carvedilol treatment, the coronary flow reserve and LV structure and function were evaluated by echocardiography. Cardiomyocytes and fibrosis were validated by histologic analysis.

RESULTS

Four-week aortic regurgitation caused a decreased LV ejection fraction and an increased LV end-systolic volume index. Regurgitation also impaired the coronary flow reserve due to an increase in the basal coronary peak diastolic velocity and velocity-time integral combined with the absence of substantial changes in the hyperemic coronary peak diastolic velocity and velocity-time integral. Four more weeks of regurgitation further deteriorated LV remodeling and coronary perfusion in the control group. In contrast, the carvedilol-treated group showed attenuated LV remodeling and a higher coronary flow reserve by decreasing the basal peak diastolic velocity and velocity-time integral without substantial changes in the hyperemic peak diastolic velocity and velocity-time integral. The coronary flow reserve and its pretreatment versus posttreatment difference were positively correlated with the pretreatment versus posttreatment LV ejection fraction and end-systolic volume index differences. In the carvedilol-treated group, subendocardial fibrosis was significantly reduced (P < .05), and the cardiomyocyte cross-sectional area tended to be smaller.

CONCLUSIONS

In mice with chronic severe aortic regurgitation, carvedilol therapy significantly improves the impaired coronary flow reserve and sufficiently attenuates adverse LV remodeling. Sustained coronary flow reserve impairment indicates progressive LV remodeling.

Cardiac rehabilitation improves coronary endothelial function in patients with heart failure due to dilated cardiomyopathy: A positron emission tomography study

BACKGROUND

Endothelial dysfunction is common in patients with heart failure and is associated with poor clinical outcome. Cardiac rehabilitation is able to enhance peripheral endothelial function but its impact on coronary vasomotion remains unknown. We aimed to evaluate the effect of cardiac rehabilitation on coronary vasomotion in patients with heart failure.

METHOD

We prospectively enrolled 29 clinically stable heart failure patients from non-ischaemic dilated cardiomyopathy and without coronary risk factors. Myocardial blood flow was quantified using (15)-O water positron emission tomography at rest and during a cold pressor test, before and after 12 weeks of cardiac rehabilitation and optimization of medical therapy.

RESULTS

Rest myocardial blood flow was significantly improved after the completion of rehabilitation compared to baseline (1.31 ± 0.38 mL/min/g vs. 1.16 ± 0.41 mL/min/g, p = 0.04). The endothelium-related change in myocardial blood flow from rest to cold pressor test and the percentage of myocardial blood flow increase during the cold pressor test were both significantly improved after cardiac rehabilitation (respectively from -0.03 ± 0.22 mL/min/g to 0.19 ± 0.22 mL/min/g, p < 0.001 and from 101.5 ± 16.5% to 118.3 ± 24.4%, p < 0.001). Left ventricular ejection fraction, plasma levels of brain natriuretic peptide, maximal oxygen consumption and the Minnesota Living with Heart Failure Questionnaire score were also significantly improved. The improvement was not related to uptitration of medical therapy.

CONCLUSIONS

Coronary endothelial function is altered in patients with heart failure due to non-ischaemic dilated cardiomyopathy. In these patients, cardiac rehabilitation significantly improves coronary vasomotion.

Intracoronary transplantation of CD34(+) cells is associated with improved myocardial perfusion in patients with nonischemic dilated cardiomyopathy

BACKGROUND

We investigated the effects of intracoronary transplantation of CD34(+) cells on myocardial perfusion in patients with nonischemic dilated cardiomyopathy (DCM).

METHODS AND RESULTS

We enrolled 21 patients with DCM (left ventricular ejection fraction [LVEF] <40%, New York Heart Association functional class III) who underwent peripheral stem cell mobilization with granulocyte-colony stimulating factor (G-CSF). CD34(+) cells were collected by means of apheresis. Patients underwent myocardial perfusion imaging, and CD34(+) cells were injected in the coronary artery supplying viable segments with reduced myocardial perfusion and regional dysfunction. Myocardial perfusion imaging was repeated 6 months later. Clinical response to stem cell therapy was predefined as a change in LVEF >5%. The majority of patients were men (81%) with an overall mean age 53 ± 9 years, LVEF 25 ± 5%, and 6-minute walking distance 354 ± 71 m. Myocardial perfusion defects at rest were observed in 86% of patients and were more common in the left anterior descending territory (50%). At 6 months' follow-up, there was a significant improvement in rest myocardial perfusion scores (6.3 ± 5.8 vs 3.1 ± 4.3; P < .001), LVEF (25 ± 7% vs 29 ± 8%; P = .005), and 6-minute walking distance (354 ± 71 m vs 404 ± 91 m; P < .001). Responders to stem cell therapy had lower summed rest perfusion score at both baseline (3.2 ± 3.0 vs 9.1 ± 6.3; P = .015) and follow-up (1.0 ± 1.5 vs 5.0 ± 5.1; P = .028).

CONCLUSIONS

CD34(+) cell transplantation may lead to improved myocardial perfusion in patients with nonischemic DCM. Patients with less severe myocardial perfusion defects at baseline may have an increased likelihood to respond to intracoronary CD34(+) cell transplantation.

Recovery mismatch between myocardial blood flow and cardiac workload after physical exercise: a positron emission tomography study

AIMS

We studied the interrelation between oxygen consumption and myocardial blood flow (MBF) during recovery. MBF is directly dependent on oxygen consumption. The latter is linearly related to the heart rate-blood pressure product (RPP, bpm × mmHg), an index reflecting external cardiac work. In the immediate post-exercise period, cardiac output decreases considerably. This is expected to be paralleled by a rapid fall in oxygen demand, rendering ischaemia unlikely. Thus, the phenomenon of ST-segment depression during recovery remains unexplained.

METHODS AND RESULTS

(15)O-labelled water and positron emission tomography were used to measure MBF in 14 young healthy volunteers (mean age 27 ± 3 years) during the following study conditions: (i) at rest, (ii) during a steady submaximal supine bicycle exercise stress within the scanner, and (iii) during recovery immediately after cessation of exercise. During recovery, RPP decreased by 43% (18 768 ± 1337 vs. 11 652 ± 3224, P < 0.001). In contrast, the associated decrease in MBF (2.52 ± 0.52 vs. 1.93 ± 0.50 mL/min/g, P < 0.001) and perfusion reserve (2.68 ± 0.51 vs. 2.03 ± 0.42, P < 0.001) was significantly less pronounced (-24%, P < 0.01), indicating a relative delay in MBF recovery compared with cardiac work load.

CONCLUSION

The mismatch between a rapid decrease in cardiac workload but preserved hyperaemic response early after cessation of physical exercise suggests an uncoupling of cardiac work and MBF during recovery.

Burn-associated delayed dilated cardiomyopathy evaluated by cardiac PET and SPECT: Report of a case

Dilated cardiomyopathy is a delayed-onset and rarely reported cardiac complication of burn injury although the mechanism remains unclear. We thus report a case of dilated cardiomyopathy following severe burn injury, in which technetium 99m sestamibi single-photon emission computed tomography (SPECT), iodine-123 beta-methyl-iodophenylpentadecanoic acid SPECT and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) were performed to evaluate the pathophysiologic condition in combination with cardiac catheterization and myocardial biopsy. The cardiac PET and SPECT images showed reduced myocardial blood flow, decreased fatty acid metabolism, and increased glucose utilization in the left ventricular lateral wall in spite of normal coronary angiography, no significant cardiac fibrosis, and inflammatory cell infiltration, which suggests that myocardial ischemia due to microcirculatory disturbance in hypermetabolic state associated with burn injury might be a causative mechanism of dilated cardiomyopathy in this case. A beta blocker, bisoprolol, was successfully introduced in this patient in combination with oral inotropic agents, pimobendan and digitalis after the prolonged use of intravenous dobutamine infusion, which might have been beneficial for this patient with burn-associated dilated cardiomyopathy not only to reduce regional myocardial ischemia but also to attenuate hypermetabolic state after severe burn injury. <Learning objective: Dilated cardiomyopathy complicated with burn injury has been reported to cause a sudden attack of dyspnea and death. This case report suggests that burn-associated dilated cardiomyopathy may be caused by relative myocardial ischemia due to microvascular disturbance in hypermetabolic state associated with burn injuries and can be treated effectively with beta blockers with or without oral inotropic agents.>.

Abnormal glucose and lipid control in non-ischemic left ventricular dysfunction

BACKGROUND

Cardiovascular risk factors are classically associated with coronary atherosclerosis. We sought to investigate whether risk factors are also associated with left ventricular (LV) dilatation, contractile impairment and reduced myocardial blood flow (MBF) in patients with non-ischemic LV dysfunction.

METHODS

We studied 81 patients (59 males, age 60 ± 9 years) with mild-to-severe LV dysfunction (mean ejection fraction 37%, range 19%-50%), no history of diabetes and normal coronary arteries. Absolute MBF was measured by positron emission tomography and (13)N-ammonia at rest and after dipyridamole (0.56 mg/kg I.V. over 4 min).

RESULTS

Overt LV dysfunction (LV end-diastolic diameter >60 mm associated with LV ejection fraction <45%) was present in 42 patients (52%); severely depressed hyperemic MBF (<1.09 mL · min(-1) · g(-1)) was present in 41 patients (51%). Using multivariate logistic regression analysis, low high-density lipoprotein cholesterol (HDL-C, P < .036), newly diagnosed non-insulin-dependent diabetes or insulin-resistance (NIDD/IR, P < .019) and the use of diuretics (P = .001) were independently associated with overt LV dysfunction. Low HDL-C (P = .015) and NIDD/IR (P = .048) were also independently associated with severely depressed hyperemic MBF.

CONCLUSIONS

Low HDL-C and NIDD/IR are associated with more severe LV impairment and reduced hyperemic MBF in non-ischemic LV dysfunction.

Quantitative cardiac positron emission tomography: the time is coming!

In the last 20 years, the use of positron emission tomography (PET) has grown dramatically because of its oncological applications, and PET facilities are now easily accessible. At the same time, various groups have explored the specific advantages of PET in heart disease and demonstrated the major diagnostic and prognostic role of quantitation in cardiac PET. Nowadays, different approaches for the measurement of myocardial blood flow (MBF) have been developed and implemented in user-friendly programs. There is large evidence that MBF at rest and under stress together with the calculation of coronary flow reserve are able to improve the detection and prognostication of coronary artery disease. Moreover, quantitative PET makes possible to assess the presence of microvascular dysfunction, which is involved in various cardiac diseases, including the early stages of coronary atherosclerosis, hypertrophic and dilated cardiomyopathy, and hypertensive heart disease. Therefore, it is probably time to consider the routine use of quantitative cardiac PET and to work for defining its place in the clinical scenario of modern cardiology.

Use of carvedilol in hypertension: an update

β-blockers are effective antihypertensive agents and, together with diuretics, have been the cornerstone of pioneering studies showing their benefits on cardiovascular morbidity and mortality as a consequence of blood pressure reduction in patients with hypertension. However, evidence from recent meta-analyses have demonstrated no benefit afforded by atenolol compared with placebo in risk of mortality, myocardial infarction, or stroke, and a higher risk of mortality and stroke with atenolol/propranolol compared with other antihypertensive drug classes. Thus, the effect of these agents on cardiovascular morbidity and mortality in hypertensive patients, especially their use in uncomplicated hypertension, has remained largely controversial. However, it is recognized that the clinical studies used in these meta-analyses were mainly based on the older second-generation β-blockers, such as atenolol and metoprolol. Actually, considerable heterogeneity in, eg, pharmacokinetic, pharmacological, and physicochemical properties exists across the different classes of β-blockers, particularly between the second-generation and newer third-generation agents. Carvedilol is a vasodilating noncardioselective third-generation β-blocker, without the negative hemodynamic and metabolic effects of traditional β-blockers, which can be used as a cardioprotective agent. Compared with conventional β-blockers, carvedilol maintains cardiac output, has a reduced prolonged effect on heart rate, and reduces blood pressure by decreasing vascular resistance. Studies have also shown that carvedilol exhibits favorable effects on metabolic parameters, eg, glycemic control, insulin sensitivity, and lipid metabolism, suggesting that it could be considered in the treatment of patients with metabolic syndrome or diabetes. The present report provides an overview of the main clinical studies concerning carvedilol administered as either monotherapy or in combination with another antihypertensive or more frequently a diuretic agent, with particular focus on the additional benefits beyond blood pressure reduction.

Ischemic patterns assessed by positron emission tomography predict adverse outcome in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Although patients with idiopathic dilated cardiomyopathy (DCM) have no coronary artery disease, regional impairment of myocardial perfusion combined with preserved metabolism has been found using positron emission tomography (PET). Our aim was to assess the prognostic relevance of PET-mismatch between stress myocardial perfusion and glucose uptake on clinical outcome in DCM.

METHODS

In 24 patients with DCM who underwent both myocardial perfusion and metabolism PET scanning, "mismatch" was assessed and the association with clinical outcome (hospitalization, mortality, and heart transplantation) was investigated.

RESULTS

Mismatch was found in 16 patients (66.7%). Univariate analysis showed that the presence of mismatch was associated with adverse outcome (P = 0.03). After adjustment for sex and age, the association remained significant with an adjusted relative risk of 10.4 (95% CI 1.1-103; P = 0.04) for death, heart transplant, or hospitalization. Univariate analysis also showed that a higher extent of mismatch was significantly associated with adverse outcome (P = 0.02). After adjusting for sex and age, the association remained significant with an adjusted relative risk of 6.5 [95% CI 1.2-36; P = 0.03] for death, heart transplantation, or hospitalization.

CONCLUSION

PET stress perfusion-metabolism mismatch, indicative for ischemia, is frequently found in DCM patients and related to a poorer outcome.

Therapeutic effect of {beta}-adrenoceptor blockers using a mouse model of dilated cardiomyopathy with a troponin mutation

AIMS

Extensive clinical studies have demonstrated that beta-adrenoceptor blocking agents (beta-blockers) are beneficial in the treatment of chronic heart failure, which is due to various aetiologies, including idiopathic dilated cardiomyopathy (DCM) and ischaemic heart disease. However, little is known about the therapeutic efficacy of beta-blockers in the treatment of the inherited form of DCM, of which causative mutations have recently been identified in various genes, including those encoding cardiac sarcomeric proteins. Using a mouse model of inherited DCM with a troponin mutation, we aim to study the treatment benefits of beta-blockers.

METHODS AND RESULTS

Three different types of beta-blockers, carvedilol, metoprolol, and atenolol, were orally administered to a knock-in mouse model of inherited DCM with a deletion mutation DeltaK210 in the cardiac troponin T gene (TNNT2). Therapeutic effects were examined on the basis of survival and myocardial remodelling. The lipophilic beta(1)-selective beta-blocker metoprolol was found to prevent cardiac dysfunction and remodelling and extend the survival of knock-in mice. Conversely, both the non-selective beta-blocker carvedilol and the hydrophilic beta(1)-selective beta-blocker atenolol had no beneficial effects on survival and myocardial remodelling in this mouse model of inherited DCM.

CONCLUSION

The highly lipophilic beta(1)-selective beta-blocker metoprolol, known to prevent ventricular fibrillation via central nervous system-mediated vagal activation, may be especially beneficial to DCM patients showing a family history of frequent sudden cardiac death, such as those with a deletion mutation DeltaK210 in the TNNT2 gene.

Beta-blockers and coronary flow reserve: the importance of a vasodilatory action

Coronary flow reserve (CFR) is the maximal increase in coronary blood flow (CBF) above its resting level for a given perfusion pressure when coronary vasculature is maximally dilated. Normally, hyperaemic CBF reaches values at least 2- to 3-fold greater than resting CBF. Reduction of CFR is mainly due to epicardial coronary artery stenosis or to coronary microvascular dysfunction. CFR can be determined by several techniques that measure CBF itself (e.g. positron emission tomography) or CBF velocities (Doppler methods) from which coronary flow velocity reserve is calculated. Hyperaemic coronary vasodilation can be obtained by pharmacological agents (e.g. adenosine and dipyridamole), but also by the cold pressure test. Long-term antihypertensive treatment induces significant improvement of CFR, which is parallel to the regression of left ventricular (LV) hypertrophy. First- and second-generation beta-adrenergic receptor antagonists (beta-blockers) have shown contradictory influences on CFR. This can be explained by the interaction of the effects on CBF at rest, generally reduced by these drugs, and after hyperaemia, when minimal coronary resistance appears to be either increased or reduced. Third-generation beta-blockers (e.g. carvedilol and nebivolol), which have vasodilating capacity, improve hyperaemic CBF. This occurs as a result of a reduction in minimal resistance, which can be attributed to alpha-adrenergic blockade and/or to a nitric oxide-mediated effect. This improvement is clearly beneficial in patients with coronary artery disease and indicates an improved coronary microvascular function. Changes of CFR due to vasodilating beta-blockers improve microvascular angina pectoris or silent ischaemia in patients without epicardial artery stenosis, and are also helpful in predicting the response or the further improvement of LV function to treatment.

Enalapril and Losartan Are More Effective Than Carvedilol in Preventing Dilated Cardiomyopathy in the Syrian Cardiomyopathic Hamster

To assess the role of the renin—angiotensin (RAS) and adrenergic systems in the development and progression of dilated cardiomyopathy in the Syrian cardiomyopathic hamster (SCH), echocardiographic parameters were evaluated in 6-month-old animals after 5 months of treatment with enalapril (25 mg/kg/day) plus losartan (10 mg/kg/day), or with carvedilol (1 mg/kg/day). Cardiac output indexes (COI) increased by 53% after RAS blockade and by 20% after β-blockade in SCH. Moreover, LVEDV and LVESV decreased 30% and 62%, respectively ( P < .05) during RAS blockade, whereas ejection fraction (EF) increased by 48%. By contrast, carvedilol reduced LVESV by only 28% ( P < .05) and increased EF by only 15% ( P < .05). These results suggest that RAS activation plays a critical role in the development of cardiac dysfunction in SCH and that suppression of RAS may be more effective than β-blockade in retarding the development of cardiomyopathy in SCH. Owing to timing (pre—heart failure stage) and to the single dose protocol, the implications of this study for human subjects remain to be clarified.