Central and peripheral components of cardiac failure

An aetiology-based subanalysis of the Telerehabilitation in Heart Failure Patients (TELEREH-HF) trial

AIMS

The aim of our study was to analyse the benefits of a 9 week hybrid comprehensive telerehabilitation (HCTR) programme in heart failure (HF) patients according to aetiology, as a subanalysis of the Telerehabilitation in Heart Failure Patients (TELEREH-HF) trial.

METHODS AND RESULTS

Overall, 555 (65.3%) patients with ischaemic (IS) and 295 (34.7%) patients with non-ischaemic (NIS) HF aetiology were randomized. There were no differences between the effect of HCTR and usual care (UC) on the primary outcome of number of days alive and out of the hospital in 26 months from the time of randomization in either aetiology (Wilcoxon-Mann-Whitney test), and no heterogeneity of effect between the aetiologies was noted (van Elteren test, P = 0.746). In Cox proportional hazards regression analysis, treatment was not independently associated with the secondary outcomes. For all-cause mortality, the adjusted hazard ratio for HCTR vs. UC was 0.90 (95% confidence interval, 0.54-1.51) in IS and 1.42 (95% confidence interval, 0.69-2.94) in NIS (P interaction = 0.316). Differences between HCTR and UC in terms of change in the 6 min walk test distance and cardiopulmonary exercise test time after 9 weeks reached statistical significance in the IS arm (P = 0.015 and P < 0.001, respectively), but not in the NIS arm; however, tests of heterogeneity indicated no statistically significant differences.

CONCLUSIONS

The trial showed no difference between HCTR and UC in the primary outcome of percentage of days alive and out of the hospital for either IS or NIS aetiology. Moreover, the magnitude of changes in the clinical and functional statuses of the HF patients did not differ by aetiology. HCTR might have had beneficial effects on the 6 min walk test distance and cardiopulmonary exercise test time after 9 weeks in the IS patients; however, the effect was not statistically significantly different from that observed in the NIS patients.

TONOMETRIA DA ARTÉRIA FEMORAL EM CÃES SAUDÁVEIS E COM DOENÇA VALVAR MITRAL DEGENERATIVA CRÔNICA

Resumo A tonometria de aplanação é um método capaz de aferir a pressão sanguínea dentro de uma artéria. Além de especulações sobre a razão das variações de amplitude das ondas de pulso femoral em cães com doença degenerativa valvar mitral crônica (DVMDC), em medicina, já está demonstrado que muitos sintomas de insuficiência cardíaca em pessoas são atribuíveis a anormalidades funcionais vasculares periféricas e não estão muito associados com parâmetros hemodinâmicos centrais. Desse modo, este trabalho teve por objetivo verificar a aplicabilidade da tonometria vascular em cães, avaliar as medidas de pressão na artéria femoral de cães saudáveis e compará-las com as de cães com regurgitação mitral devido à DVMDC. Os parâmetros tonométricos ainda foram correlacionados com índices cardíacos obtidos pela ecocardiografia. Os dados foram obtidos de 10 cães saudáveis e de 10 cães com DVMDC com regurgitação mitral à ecocardiografia. Observou-se que o período de pré-condução da onda de pulso foi significantemente menor nos animais com DVMDC do que nos saudáveis. Houve uma forte correlação entre a pressão sistólica da artéria femoral com parâmetros determinantes da função sistólica do coração nos animais saudáveis. A tonometria por aplanação da artéria femoral mostrou-se uma técnica aplicável em cães.

Muscular arterial impedance in dogs with chronic degenerative mitral valve disease

Systemic vascular impedance represents the retrograde strength of the blood flow to the left ventricle, thus it is one of the main compounds of afterload. Mitral regurgitation is markedly sensitive to afterload alterations. The purpose of this study was to evaluate muscular arterial impedance in dogs with chronic degenerative mitral valve disease (CDMVD) by use of duplex Doppler ultrasonography (DDU), since its technique there was not used before to determine impedance index in dogs with CDMVD. For this purpose, ten healthy dogs and ten dogs with CDMVD were used. Some parameters related to blood flow impedance in the common femoral artery were measured by DDU: pulsatility index (PI), resistance index (RI), high-resistance index (HRI), and acceleration velocity (AC) and deceleration velocity (DC) of the systolic peak. The results showed that RI and HRI were significantly higher in animals with CDMVD than in healthy animals. These findings showed that DDU provides quantitative data related to vascular impedance. Broader studies may therefore provide new aspects related to physiopathology and therapy in CDMVD patients.

Effects of sedation with acepromazine maleate and buprenorphine hydrochloride on femoral artery blood flow in healthy dogs

The purpose of this study was to qualify and quantify the femoral artery blood flow by duplex Doppler ultrasonography (DDU) in healthy dogs, before and after the administration of a combination of acepromazine maleate and buprenorphine hydrochloride (ACP-BPN). Seven healthy adult mongrel dogs and three adult beagles were used. Heart rate, arterial blood pressure and measurement of femoral artery blood flow by DDU were also recorded. The DDU measurements were: femoral artery diameter (FAD), peak systolic velocity (PSV), early retrograde (EDV) and end diastolic velocities (EnDV), mean velocity (BMV), pulsatility index (PI), flow velocity integral (FVI) and femoral blood flow (FBF). After 30 min, combination ACP-BPN was administered intramuscularly, and all the measurements were recorded again. The ACP-BPN protocol induced a significant decrease in systolic, mean, and diastolic arterial blood pressure, and heart rate. A significant increase in peak systolic velocity and integral flow velocity integral of the femoral blood were obtained. The Doppler spectra of the blood flow in the femoral artery revealed a spectral dispersion pattern after ACP-BPN administration in all the dogs. These results demonstrate that despite quantitative and qualitative changes, the overall femoral blood flow (FBF) is not significantly modified.

Alterations in the large peripheral circulation in dogs with heart failure

The femoral artery is responsible for perfusion of a large muscular region that can be involved in the exercise intolerance shown by dogs with spontaneous heart failure. The objective of the present study was to evaluate blood flow in the femoral artery by transcutaneous duplex Doppler ultrasonography (TDU) in 50 healthy dogs and 50 dogs with spontaneous heart failure. The group of dogs with heart disease was divided according to the functional class of the heart failure. The TDU measurements were: peak systolic velocity (PSV), early retrograde (EDV) and end diastolic velocities (EnDV), mean velocity (MV), pulsatility index (PI), resistivity index (RI) and femoral flow volume (FFV). In healthy dogs, PSV and FFV were significantly higher than in dogs with heart disease. FFV was reduced mainly in patients with moderate and severe heart failure. TDU allowed for non-invasive detection and quantification of pathological alterations in peripheral hemodynamics.

Left ventricular chamber stiffness at rest as a determinant of exercise capacity in heart failure subjects with decreased ejection fraction

Impaired exercise tolerance, determined by peak oxygen consumption (V̇o2 peak), is predictive of mortality and the necessity for cardiac transplantation in patients with chronic heart failure (HF). However, the role of left ventricular (LV) diastolic function at rest, reflected by chamber stiffness assessed echocardiographically, as a determinant of exercise tolerance is unknown. Increased LV chamber stiffness and limitation of V̇o2 peak are known correlates of HF. Yet, the relationship between chamber stiffness and V̇o2 peak in subjects with HF has not been fully determined. Forty-one patients with HF New York Heart Association [(NYHA) class 2.4 ± 0.8, mean ± SD] had echocardiographic studies and V̇o2 peak measurements. Transmitral Doppler E waves were analyzed using a previously validated method to determine k, the LV chamber stiffness parameter. Multiple linear regression analysis of V̇o2 peak variance indicated that LV chamber stiffness k ( r2 = 0.55) and NYHA classification ( r2 = 0.43) were its best independent predictors and when taken together account for 59% of the variability in V̇o2 peak. We conclude that diastolic function at rest, as manifested by chamber stiffness, is a major determinant of maximal exercise capacity in HF.

Central and peripheral components of chronic heart failure: determinants of exercise tolerance

This study sought to determine the relationship between myocardial dysfunction and peripheral haemodynamic disorders to exercise intolerance in patients with chronic heart failure (CHF). Seventeen patients with mild to moderate CHF (peak oxygen consumption (VO2) >16 ml/min/kg) and 13 with severe CHF (peak VO2 <16 ml/min/kg) underwent invasive (Swan-Ganz) cardiopulmonary exercise testing and forearm venous occlusion plethysmography at rest and during maximal dilatation in reactive hyperaemia. There was a shift from central to peripheral haemodynamic factors limiting exercise, suggesting an increasing importance of peripheral factors in parallel to the progression of CHF. In mild to moderate CHF peak VO2 was closely related to central haemodynamics (r = 0.57 for cardiac index at rest; r = 0.76 for cardiac index at maximal workload; r = -0.54 for right arterial pressure at maximal workload; all p<0.05) and poorly correlated with peripheral haemodynamics (blood flow, vascular resistance and venous tone). In contrast, in severe CHF peak VO2 was closely related to peripheral haemodynamic factors (r = 0.79 for forearm blood flow; r = -0.82 for vascular resistance; r = -0.77 for venous tone; all p<0.05) and less to central ones. Thus, exercise tolerance of patients with mild to moderate CHF is predominantly determined by central haemodynamic factors, notably by the cardiac index. In severe CHF peripheral factors assume ever greater importance in the determining of exercise capacity.

Cardiac metaiodobenzylguanidine uptake in patients with moderate chronic heart failure: relationship with peak oxygen uptake and prognosis

OBJECTIVES

This prospective study was undertaken to correlate early and late metaiodobenzylguanidine (MIBG) cardiac uptake with cardiac hemodynamics and exercise capacity in patients with heart failure and to compare their prognostic values with that of peak oxygen uptake (VO2).

BACKGROUND

The cardiac fixation of MIBG reflects presynaptic uptake and is reduced in heart failure. Whether it is related to exercise capacity and has better prognostic value than peak VO2 is unknown.

METHODS

Ninety-three patients with heart failure (ejection fraction <45%) were studied with planar MIBG imaging, cardiopulmonary exercise tests and hemodynamics (n = 44). Early (20 min) and late (4 h) MIBG acquisition, as well as their ratio (washout, WO) were determined. Prognostic value was assessed by survival curves (Kaplan-Meier method) and uni- and multivariate Cox analyses.

RESULTS

Late cardiac MIBG uptake was reduced (131+/-20%, normal values 192+/-42%) and correlated with ejection fraction (r = 0.49), cardiac index (r = 0.40) and pulmonary wedge pressure (r = -0.35). There was a significant correlation between peak VO2 and MIBG uptake (r = 0.41, p < 0.0001). With a mean follow-up of 10+/-8 months, both late MIBG uptake (p = 0.04) and peak VO2 (p < 0.0001) were predictive of death or heart transplantation, but only peak VO2 emerged by multivariate analysis. Neither early MIBG uptake nor WO yielded significant insights beyond those provided by late MIBG uptake.

CONCLUSIONS

Metaiodobenzylguanidine uptake has prognostic value in patients with wide ranges of heart failure, but peak VO2 remains the most powerful prognostic index.

Safety of calcium antagonists in patients with congestive heart failure

Continuing high morbidity and mortality have spurred an ongoing search for new therapeutic agents for patients with congestive heart failure. Calcium antagonists (CAs) have been under active investigation in patients with heart failure since their introduction into clinical medicine, because their anti-ischemic and vasodilator properties were thought to be of potential benefit in this patient population. However, review of published clinical trials of CAs in patients with heart failure reveals that some of these drugs are associated with detrimental effects, including acute hemodynamic deterioration, increased symptoms of heart failure, and increased mortality. The adverse effects of short-acting CAs in patients with heart failure include negative inotropic effects and neurohormonal activation. Long-acting CAs, such as amlodipine and felodipine, had fewer negative inotropic effects, showed less evidence of neurohormonal activation, and were better tolerated in clinical trials. Amlodipine, in combination with an angiotensin-converting enzyme inhibitor, had a neutral effect in patients with ischemic heart failure and an unexplained benefit in a subgroup of patients with non-ischemic cardiomyopathy. Although the preliminary experience with long-acting dihydropyridine CAs in heart failure has been encouraging, safety concerns raised by past trials dictate that no CA can be recommended for the treatment of heart failure at this time.

The role of endothelium-derived vasoactive substances in the pathophysiology of exercise intolerance in patients with congestive heart failure

The vascular endothelium releases vasoactive substances that appear to play an important role in the normal regulation of peripheral vasomotor tone. Nitric oxide, endothelins, prostaglandins, and other endothelium-derived vasodilating and vasoconstricting factors are released by the vascular endothelium in response to a diverse array of hormonal, pharmacologic, chemical, and physical stimuli. Shear stress, produced by pulsatile blood flow at the endothelial cell luminal surface, alters endothelial production of several endothelium-derived vasoactive substances, which may contribute to regional regulation of skeletal muscle blood flow during exercise. Abnormal vascular endothelium function has been shown in both experimental and clinical heart failure. Preliminary data suggest that abnormalities of endothelial function may contribute to increased peripheral vasomotor tone during exercise in patients with congestive heart failure.

The push, the pull and the periphery

If the failing left ventricle could be given an effective push, other approaches to the treatment of heart failure would not be needed. We have inotropes only for short-term parenteral use. We have no safe inotrope for chronic oral use. The effect of digitalis is only feeble and the phosphodiesterase inhibitors seem to increase mortality from sudden death. Diuretics are dramatic for acute pulmonary oedema and the mainstay for chronic fluid retention but do not improve the pump and by reducing blood volume stimulate the renin angiotensin system to vasoconstriction, further fluid retention and hypokalaemia. Nitrates drop pre-load without reducing blood volume but tolerance is a problem and stroke volume does not increase. Reduction of afterload helps the failing ventricle to empty, the pull and output increases. The angiotensin converting enzyme inhibitors (ACEI) are now the cornerstone of heart failure treatment, reducing mortality in severe heart failure (CONSENSUS) and superior to standard vasodilator therapy (V-HeFT-2) at improving the survival of patients with mild to moderate heart failure. ACEI can reduce the incidence of ventricular ectopy and probably do this through improving left ventricular function, from decreasing sympathetic tone, reducing myocardial oxygen demand or increasing serum potassium but ACEI did not diminish the incidence of sudden death in the SOLVD trial despite reducing mortality. Disappointingly little improvement in exercise tolerance and persistence of chronic fatigue in heart failure concentrated attention on the periphery.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical analysis of methods for assessing regional blood flow and their reliability in clinical medicine

The advantages and inadequacies of the currently available techniques to measure regional blood flow in the lower limbs are being reviewed. Thermodilution technique and local 133xenon washout technique have the advantage of allowing determination of blood flow during exercise, while venous occlusion plethysmography and pulsed-Doppler duplex ultrasonography only allow determination of blood flow at rest. Overall, measurements of lower limb blood flow are not highly reproducible by any technique, and the variability in measurements of regional blood flow should lead to careful interpretation of derived parameters such as vascular conductance and resistance. Determination of vascular input impedance by Fourier analysis of pressure data, recorded with high fidelity catheter, and flow velocity measurements obtained transcutaneously by Doppler ultrasonography, may offer a more accurate quantitative analysis of the characteristics of the lower limb vascular system.

Theoretical considerations in the use of dynamic cardiomyoplasty to treat dilated cardiomyopathy

Clinical data describing the hemodynamic benefits of cardiomyoplasty are inconclusive, and there has not been any study detailing the mechanisms by which dynamic cardiomyoplasty may improve the functional and mechanical impairments of the failing heart. The left ventricle in dilated cardiomyopathy is characterized by increased end-diastolic volume, inadequate systolic myocardial wall thickening, increased wall stress, and decreased stroke volume. Based on experimental and preliminary clinical data, we propose that cardiac assistance by dynamic cardiomyoplasty is the consequence of enhanced volume translocation rather than increased potential for pressure generation. A small augmentation of dimensional shortening results in a large increment of stroke volume because of the enlarged resting chamber volume. Key geometric effects are enhanced systolic chamber shortening and increased wall thickening, resulting in a net decrease of myocardial wall stress. The contractile skeletal muscle may improve myocardial mechanics, and normalization of the afterload mismatch may be an important mechanism by which dynamic cardiomyoplasty augments cardiac output.

Effects of phosphodiesterase inhibition on skeletal muscle vasculature

The pathophysiology of the syndrome of congestive heart failure (CHF) includes 2 major components that closely interact. The first one is a reduction in ventricular performance, which is manifested initially during exercise and is later present at rest. The second one involves abnormalities of the peripheral circulation and organs, which become gradually more prominent and lead ultimately to symptoms. The exercise capacity of patients with chronic CHF is limited not only by an inadequate increase in cardiac output and an excessive increase in ventricular filling pressure, but also by a fixed vasodilatory response to exercise. Although the role of increased activity of the sympathetic and renin-angiotensin-aldosterone systems in the derangements of the peripheral circulation has been extensively investigated, the structural abnormalities of the arterial wall have received little emphasis in patients with CHF. Chronic reduction of the cardiac output may lead to endothelium-dependent reduction in arterial diameter and vasomotor response, which may in turn increase systemic vascular resistance and further reduce cardiac output. Therapeutic agents should be characterized by their acute and chronic effects not only on ventricular performance, but also on the peripheral circulation. More specifically, when one is concerned with the effect of a therapeutic intervention on exercise capacity, evaluation of its direct and indirect effects on the skeletal muscle vasculature is particularly important. Accordingly, the effects of phosphodiesterase inhibition on vascular smooth muscle tone and skeletal muscle vasculature are reviewed. In addition, the potential of phosphodiesterase inhibition to reverse structural abnormalities of the arterial wall is discussed.

Coronary artery spasm: involvement of small intramyocardial branches

A study was conducted to determine if the small (resistance) vessels of the coronary circulation could undergo spasm comparable to that of the major conductance (epicardial) arteries which in the rat measure 275-300 micron in diameter. This information may be relevant to the growing evidence of ischemic myocardial disease without significant coronary atherosclerosis or even spasm of the larger vessels. Vascular corrosion casts of the coronary circulation were prepared in the rat 20 min after intravenous injection of arginine vasopressin, a powerful coronary constrictor substance, under continuous electrocardiographic monitoring. Electrocardiographic changes observed consisted of S-T segment elevation and conduction disturbances, implying ischemic effects on the myocardium. Corrosion casts revealed spasm of smaller arteries only (50-150 micron diameter). Controls (vehicle-injected or untreated) showed no abnormalities of the coronary vasculature. These results suggest that myocardial vessels of this size are comparable in their potential for spasm to the large conductance arteries. Similar findings in patients involving smaller vessels could explain ischemic myocardial events in the absence of significant spasm, or organic stenosing pathology of major coronary arteries. As a corollary, it is suggested that the term "coronary artery spasm" could be enlarged in its definition to include other levels of the coronary circulation rather than that of the large conductance arteries alone.

Chronic congestive heart failure. Where have we been? Where are we heading?

Chronic congestive heart failure is a frequently occurring disease associated with an impaired quality of life and significant mortality rate. Progress has been made in dissecting the pathophysiologic changes of congestive failure and in using vasodilators, newer positive inotropic agents, and other treatment modalities. Despite these advances, the overall mortality rate from congestive heart failure has not decreased. Further, many unanswered questions remain: How and why does a myocardial cell die? How should quality of life be measured? When should vasodilators and positive inotropic agents be given? What role do receptors play in pathogenesis and therapy? Can sudden death in heart failure be prevented? These and other questions will provide the stimulus for further studies in congestive heart failure.