Investigations of the peripheral vascular mechanisms implicated in congestive heart failure by the non-invasive evaluation of radial artery compliance and reactivity

Cerebral blood flow changes during intermittent acute hypoxia in patients with heart failure

Objective Heart failure (HF) is associated with intermittent hypoxia, and the effects of this hypoxia on the cardiovascular system are not well understood. This study was performed to compare the effects of acute hypoxia (10% oxygen) between patients with and without HF. Methods Fourteen patients with chronic HF and 17 matched control subjects were enrolled. Carotid artery changes were examined during the first period of hypoxia, and brachial artery changes were examined during the second period of hypoxia. Data were collected at baseline and after 2 and 4 minutes of hypoxia. Norepinephrine, epinephrine, dopamine, and renin were measured at baseline and after 4 minutes hypoxia. Results The carotid blood flow, carotid systolic diameter, and carotid diastolic diameter increased and the carotid resistance decreased in patients with HF. Hypoxia did not change the carotid compliance, distensibility, brachial artery blood flow and diameter, or concentrations of sympathomimetic amines in patients with HF, but hypoxia increased the norepinephrine level in the control group. Hypoxia increased minute ventilation and decreased the oxygen saturation and end-tidal carbon dioxide concentration in both groups. Conclusion Hypoxia-induced changes in the carotid artery suggest an intensification of compensatory mechanisms for preservation of cerebral blood flow in patients with HF.

Elastic properties of peripheral arteries in heart failure patients in comparison with normal subjects

Understanding the change in elastic properties of peripheral arteries in heart failure patients is of particular importance, especially when compared with normal subjects. To investigate factors associated with their difference, 40 normal subjects and 60 heart failure patients were studied. Electrocardiograms, carotid pulses and radial pulses were simultaneously recorded to determine carotid-radial pulse transit time (carotid-radial PTT), arm pulse wave velocity (PWV), and arterial volume distensibility. In comparison with normal subjects, carotid-radial PTT was lower by 8 ms in heart failure patients, arm PWV higher by 1.4 m/s, and peripheral arterial distensibility lower by 0.04 % per mmHg (all significant, P < 0.01). Peripheral arterial distensibility was significantly related to systolic blood pressure (SBP) and to left ventricular ejection fraction (LVEF) for heart failure patients (both P < 0.001), but the relationship for the normal group was not statistically significant (both 0.05 < P<0.1). Ageing had a significant inverse relationship with arterial distensibility in normal subjects (P < 0.05), but not in heart failure patients (P = 0.59). No subject in the normal group had an arterial distensibility lower than 0.1 % per mmHg, in comparison with 28 % (17/60) in the heart failure group. Peripheral arterial distensibility has been shown to be significantly lower in heart failure patients in comparison with normal subjects. High SBP and low LVEF were the main factors associated with low arterial distensibility in heart failure patients.

Interaction between pulse wave velocity, augmentation index, pulse pressure and left ventricular function in chronic heart failure

Pulse wave velocity (PWV), the carotid augmentation index (AIx), and pulse pressure (PP) may be prognostic factors in heart failure, but the possible influence of the ejection fraction (EF) and other simple haemodynamic variables on them has not been investigated in this setting. Noninvasive methods were used to measure carotid-radial (CR), carotid-femoral (CF) PWV and AIx, and brachial PP, in 135 consecutive patients with stable symptomatic chronic heart failure. The patients were divided into two groups, with preserved (>or=40%) or reduced (<40%) EF. CF-PWV, AIx and PP were lower in the decreased EF group (8.85+/-2.77 versus 10.60+/-2.75 m/s, P<0.001; 121+/-21 versus 132+/-24, P=0.009 and 41+/-19 versus 67+/-17 mmHg, P<0.001), but CR-PWV values were similar regardless of the EF status. These results were not modified after adjustment for age and sex. Multiple regression analysis showed that AIx and PP were systematically related to time domain parameters (heart rate or ejection duration) and EF, whatever the group. CF-PWV was weakly related to time domain values and unrelated to mean blood pressure (BP) or EF in the preserved EF group, whereas it was related to both mean BP and EF in the low EF group. In conclusion, whatever the EF level, PP and AIx were strongly modulated in the time domain, by pressure and by the EF level. The same relationships were found with CF-PWV, but only in the reduced EF group. Whether CF-PWV is the best prognostic factor in patients with 'diastolic' heart failure must be confirmed in a prospective study.

Radial, carotid and aortic distensibility in congestive heart failure: effects of high-dose angiotensin-converting enzyme inhibitor or low-dose association with angiotensin type 1 receptor blockade

objectives; The aim of this study was to determine whether in patients with congestive heart failure (CHF) a distensibility (Dist) reduction: 1) similarly occurs in different arteries; 2) is related to CHF severity; and 3) is reversible with treatment. background: Several studies suggest that CHF is accompanied by a reduced arterial Dist.

METHODS

We measured diameter in radial artery, carotid artery (CA) and abdominal aorta (AO) by echotracking. Distensibility was obtained by relating it to blood pressure. Data were collected in 30 patients with CHF (New York Heart Association functional class I to III) under standard treatment with diuretic, digitalis and angiotensin-converting enzyme (ACE) inhibitor in whom CHF severity was assessed by maximum oxygen consumption (VO(2)max) percentage and in 30 age- and gender-matched controls. Patients with CHF were then randomized to maintain standard treatment (n = 10), double the ACE inhibitor dose (n = 10) or add an angiotensin II antagonist (n = 10) and restudied after two months.

RESULTS

Distensibility was markedly reduced in the CHF group in all three vessels (p < 0.01), CA and AO Dist being related to CHF severity (p < 0.05). After two months, Dist did not change in the group maintained under standard treatment, but it increased significantly (p < 0.05) and similarly when the ACE inhibitor dose was doubled or an angiotensin II antagonist was added.

CONCLUSIONS

Congestive heart failure is characterized by a reduction of Dist of large-elastic and middle-sized muscular arteries. The reduction of large-elastic artery Dist is related to the CHF severity. These alterations can be reversed by drugs, effectively interfering with the renin-angiotensin system either at the ACE or at the angiotensin receptor level.

Brachial artery elastic mechanics in patients with heart failure

Studies of arterial elasticity in patients with heart failure (HF) have produced varying results. In addition, the direct effects of smooth muscle relaxation on arterial wall mechanics in these patients have not been well characterized. Nineteen patients with New York Heart Association class II to IV HF and 17 age- and size-matched normal subjects were studied by using a recently validated technique for measuring brachial arterial wall mechanics over a wide pressure range. The left brachial artery was imaged through a water-filled blood pressure cuff by use of an ultrasound wall-tracking system at baseline and after 0.4 mg sublingual nitroglycerin (NTG). Simultaneous radial artery pressure waveforms were recorded by tonometry. Transmural pressure (TP) was reduced by increasing water pressure in the cuff. Baseline area, compliance, and pulse wave velocity versus TP curves were similar in the normal subjects and the patients with HF. The incremental elastic modulus versus TP curve tended to be lower in the patients with HF. The wall-to-lumen ratio was increased in HF (P=0.05). NTG significantly shifted the area versus TP (P<0.001) and compliance versus TP (P<0.05) curves upward and the pulse wave velocity versus TP (P<0.05) curve downward in both groups. NTG also significantly (P<0.001) shifted the stress versus strain curve to the right in both groups but did not alter the incremental elastic modulus versus TP curve. We conclude that the brachial arterial wall-to-lumen ratio is increased in HF. This finding occurs together with a trend toward reduced arterial stiffness such that overall mechanical behavior of the brachial artery is preserved. Smooth muscle relaxation with NTG produces similar improvements in brachial arterial wall mechanics in normal subjects and in patients with HF.

Alterations in the peripheral circulation in patients with mild heart failure

OBJECTIVE

In patients with severe heart failure, compensatory mechanisms fail to provide adequate blood supply to the peripheral circulation, especially when the metabolic need is increased. The aim of this study was to assess alterations in the peripheral circulation in patients with mild heart failure using ultrasound Doppler.

METHODS

In 19 controls and in 11 patients with mild heart failure, Doppler spectra were recorded from the carotid, the brachial and the femoral artery at rest and, from the latter two arteries, during post-occlusive reactive hyperemia. Parameters derived from these Doppler spectra were used to make comparisons between both groups.

RESULTS

At rest, the duration of the acceleration of blood was shorter in controls, the acceleration was steeper in controls and the deceleration duration was longer in controls as compared to the patients. Differences in the response to reactive hyperemia were only observed in the common femoral artery.

CONCLUSIONS

In patients with mild heart failure, significant alterations in the peripheral circulation were observed especially for the femoral artery. These changes are caused by the impairment of the left ventricular function and by adjustments in the compensatory mechanism of the peripheral circulation.

Enhanced Ca2+-induced contractions and attenuated alpha-adrenoceptor responses in resistance arteries from rats with congestive heart failure

AIM

The aim of the present study was to examine the role of Ca2+-mediated contractile responses in isolated mesenteric resistance arteries from rats with congestive heart failure (CHF).

METHODS

Heart failure was induced by ligation of the left coronary artery. Rats exposed to the same surgical procedure except ligation served as controls (Sham). The following experiments were conducted: (1) passive increase in radial stretch (the length-tension relationship) in Ca2+-free and in depolarizing high K+-solution; (2) the contractile responses to external application of Ca2+ and high K+-solutions in the presence of nifedipine and phentolamine; and (3) a histological evaluation of CHF and Sham vessels.

RESULTS

The length-tension induced response in Ca2+-free buffer solution was significantly lower in arteries from CHF rats, starting at a very low tension (0.9+/-0.2 mN/mm for heart failure and 1.7+/-0.2 mN/mm for Sham). This difference, but at a higher degree of stretch, was also present in K+-activated vessels. The external application of Ca2+ in K+-depolarized vascular segments in the presence of phentolamine (1 microM) induced an enhanced contractile response in arteries from CHF rats compared with Sham (4.8+/-0.3 mN/mm and 3.6+/-0.6 mN/mm, respectively, P=0.059). In the absence of phentolamine the reverse response was found (4.0+/-0.4 mN/mm and 5.7+/-0.3 mN/mm for CHF vs. Sham respectively, P=0.035). Application of increasing concentrations of K+-solution induced a stronger contractile response in Sham compared with CHF arteries (Sham 4.9+/-0.4 and heart failure 4.0+/-0.3, P=0.04). Microscopic examination of vessels yielded no difference in gross morphology, media thickness or wall to lumen ratio between CHF and Sham arteries.

CONCLUSION

The results indicate an attenuation of alpha-adrenoceptors and a difference of Ca2+-mediated vascular contractility in resistance arteries of congestive heart failure rats.

Superiority of endothelin-1 over norepinephrine in exercise-induced alterations of the conduit artery tone of the non-exercised arm in patients with chronic heart failure

This study is aimed at examining the relative importance of norepinephrine and endothelin-1 in treadmill exercise-induced changes in brachial arterial tone of the non-exercised arm in patients with chronic heart failure (CHF). Brachial artery diameter and blood flow were measured before and after exercise in eight healthy volunteers and 18 patients with stable chronic heart failure by high-resolution ultrasound. Maximal exercise resulted in brachial artery dilatation in controls (4.42+/-0.39 vs. 4.77+/-0.39 mm; P<0. 0001) in contrast to constriction seen in the patients (5.27+/-0.67 vs. 5.12+/-0.66 mm; P=0.07). Both groups demonstrated a significant increase in blood flow after exercise. The pre-exercise (2.83+/-0.76 vs. 1.69+/-0.15 pmol/l; P=0.0004), post-exercise (4.15+/-1.5 vs. 2. 02+/-0.34 pmol/l; P=0.0004) and the percent increase (47.15+/-32.5 vs. 19.0+/-10.5%; P=0.02) in endothelin-1 levels were significantly greater in patients than in controls. In contrast to endothelin-1, the exercise-induced percent increase in norepinephrine was greater in controls than patients (100.7+/-51.8 vs. 49.8+/-43.4%; P=0.01). The percent change in the diameter of the brachial artery in response to maximal exercise was significantly correlated to pre- (r=0.634; P=0.003) and post-exercise (r=0.467; P=0.05) endothelin-1 levels in patients but not in controls [pre-exercise (r=0.07; P=0. 86), post-exercise (r=0.310; P=0.47)]. The change in the diameter of the brachial artery did not correlate with pre- or post-exercise plasma norepinephrine levels in either group. These findings suggest that endothelin-1 is potentially more important than norepinephrine in contributing exercise-induced brachial artery constriction in patients with chronic heart failure.