The effect of upright posture on right ventricular volumes in patients with and without heart failure

The right ventricle

The healthy right ventricle (RV) has a thin-walled structure compared to the thick-walled left ventricle (LV). It has a complex shape that appears crescentic when viewed in cross section and triangular when viewed from the side.

The effect of posture on Cheyne-Stokes respirations and hemodynamics in patients with heart failure

STUDY OBJECTIVES

Cheyne-Stokes respirations occur in 40% of patients with heart failure. Orthopnea is a cardinal symptom of heart failure and may affect the patient's sleeping angle. The objective of this study was to assess the respiratory and hemodynamic response to sleeping angle in a group of subjects with stable heart failure.

DESIGN

Twenty-five patients underwent overnight polysomnography with simultaneous and continuous impedance cardiographic monitoring. Sleeping polysomnographic and impedance cardiographic data were recorded.

SETTING

The study was conducted in a sleep center.

PATIENTS

All 25 patients had clinically stable heart failure and left ventricular ejection fractions < 40%.

INTERVENTIONS

The patients slept at 0 degrees, 15 degrees, 30 degrees, and 45 degrees in random order.

MEASUREMENTS AND RESULTS

Seventeen patients had Cheyne-Stokes apneas (index > 5/h) and 23 patients had hypopneas (index > 5/h). The hypopnea index showed no response to sleeping angle. The Cheyne-Stokes apnea index decreased with increasing sleeping angle (P < 0.001). This effect was seen only during supine sleep and non-rapid eye movement sleep and was absent in non-supine sleep, rapid eye movement sleep, and during periods of wakefulness. Thoracic fluid content index and left ventricular hemodynamics measured by impedance cardiography showed no response to sleeping angle.

CONCLUSIONS

Changing the heart failure patient's sleeping angle from 0 degrees to 45 degrees results in a significant decrease in Cheyne-Stokes apneas. This decrease occurs on a constant base of hypopneas. The changes in Cheyne-Stokes apneas are not related to changes in lung congestion and left ventricular hemodynamics.

CHF: circulatory homeostasis gone awry

The role of the renin-angiotensin-aldosterone system (RAAS) is integral to salt and water retention, particularly by the kidneys. Over time, positive sodium balance leads first to intra- and then to extravascular volume expansion, with subsequent symptomatic heart failure. This report examines the role of the RAAS in regulating a less well recognized component essential to circulatory homeostasis--central blood volume. The regulation of central blood volume draws on integrative cardiorenal physiology and a key role played by the RAAS in its regulation. In presenting insights into the role of the RAAS in regulating central blood volume, this review also addresses other sodium-retaining states with a predisposition to edema formation, such as cirrhosis and nephrosis.

Chagas' cardioneuropathy: effect of ganglioside treatment in chronic dysautonomic patients--a randomized, double-blind, parallel, placebo-controlled study

To date, there is no effective pharmacologic treatment for Chagas' cardioneuropathy, one of the most common causes of congestive heart failure and sudden death in the world. Fifty-eight adults with positive serology for Chagas' disease and abnormal autonomic nervous system tests participated in this placebo-controlled clinical trial with Cronassial (mixed gangliosides), 40 mg daily intramuscular injection for 4 or 8 weeks. We measured postural response (heart rate, systolic and diastolic arterial blood pressure changes in response to standing); heart rate changes induced by cough and hyperventilation reflex tests; dizziness on standing; number of stress-induced arrhythmias; and periodic acid-Schiff (PAS)-positive T-lymphocyte percentage in blood samples. Cronassial is safe and significantly improves systolic blood pressure (p = 0.050) and double product responses to postural stress (p = 0.028), hyperventilation heart rate response (p = 0.007), frequency of dizziness episodes (p less than 0.001), number of arrhythmias (p = 0.033), and percentage of PAS-positive T-lymphocyte counts (p less than 0.001) compared with placebo.

Differentiation of cardiac murmurs by dynamic auscultation

The techniques described in this monograph will aid in the accurate identification of the origin of a cardiac murmur or abnormal heart sound. They do not necessarily reveal the presence or severity of cardiac disease. No maneuver is 100% accurate in elucidation of cardiac abnormalities, and a given maneuver's effectiveness varies in its application. The systematic application of a combination of maneuvers improves the accuracy of diagnosis. Auscultatory findings must be interpreted with consideration of the total clinical examination including history, other physical findings, ECG, chest x-ray, and possibly an echocardiogram. Thus, the careful physiological approach to the physical examination represents a powerful noninvasive tool that can be used in combination with other information to accurately diagnose cardiac disease in many patients and efficiently direct further evaluation when necessary.

Head-down tilt as a physiological diuretic in normal controls and in patients with fluid-retaining states

The effect of the sitting, supine, supine with legs elevated 10 degrees, and 10 degrees head-down tilt postures on renal fluid and electrolyte handling was investigated in 14 patients with hypoalbuminaemic fluid-retaining states and in 14 normal individuals. Basal (sitting) urine volume, creatinine clearance, and urinary electrolyte levels were significantly lower in patients than in controls. In patients the values of these variables increased progressively from the sitting to the supine to the legs elevated to the head-down postures. The percentage rise was higher in patients than in controls, to the extent that, in the head-low position, only creatinine clearance values remained lower in patients than in controls. The head-down posture acts as a physiological diuretic, enhancing diuresis by improving renal function in normal individuals and in patients with ascites and oedema due to hypoalbuminaemia; it also corrects the abnormal fluid and sodium retention in these patients.

An analysis of the determinants of exercise performance in congestive heart failure

Twenty-nine patients with chronic congestive heart failure underwent symptom-limited maximal exercise to define the determinants and predictors of exercise capacity in this condition. Clinically, the combination of age, cardiothoracic ratio, and left ventricular displacement was moderately predictive of exercise capacity (R2 = 0.44, p = 0.004). Noninvasive and angiographic measurements of ventricular performance failed to predict maximal exercise duration. Resting systemic and pulmonary arteriolar resistances correlated modestly with maximal effort tolerance (supine: R2 = 0.25, p = 0.02; upright: R2 = 0.38, p = 0.002). At a predetermined level of submaximal exercise, changes in heart rate and pulmonary arteriolar resistance plus the absolute value of systemic arteriolar resistance correlated moderately with exercise duration (R2 = 0.44, p = 0.003). For all parameters examined, exercise capacity was most reliably determined during the transition from submaximal to maximal exercise through the combination of changes in heart rate and stroke volume and the exercise end point value of systemic arteriolar resistance (R2 = 0.87, p = 0.0001). Exercise capacity in chronic cardiac failure appears to be best explained by the patient's ability to increase heart rate and stroke volume beyond a set submaximal stage of exercise. Excessive vascular resistances may further restrain cardiac performance and the delivery of blood to exercising structures during exhaustive exercise.

Effect of acute standing and prolonged upright activity on left ventricular hemodynamics, systolic and diastolic intervals, and QT-QS2 relationship

It is generally accepted that upright posture decreases preload and afterload, which could alter left ventricular (LV) performance. It is not known if changes occurring with acute standing persist after prolonged ambulatory activity (amb-act). In seven normal subjects echocardiographic end-diastolic and end-systolic diameters, percent shortening of the internal diameter (% delta D) and end-systolic wall stress (ES-WS), radionuclide diastolic volume and ejection fraction, preejection period over left ventricular ejection time (PEP/LVET), and diastolic time and QT-QS2 were measured supine, within 1 to 2 minutes after standing and after prolonged (60 minutes) amb-act. In addition, serial measurements were performed in PEP/LVET for 105 minutes at 15-minute intervals. With acute standing, end-diastolic diameter, diastolic volume, and ES-WS decreased (p less than 0.01); heart rate and PEP/LVET increased (p less than 0.01); while % delta D and ejection fraction remained unchanged. There was an inverse correlation between change in PEP/LVET and diastolic diameter (r = -0.59), but no correlation between PEP/LVET and ES-WS. The diastolic time per beat and per minute decreased (375 +/- 115 msec from 519 +/- 176 msec [p less than 0.01] and 31.3 +/- 4.2 sec/min from 33.7 +/- 4.5 sec/min [p less than 0.01]). The QT-QS2 increased when compared to supine (-7 +/- 7.6 msec from -22 +/- 7.7 msec [p less than 0.005]), but the QT-QS2 relationship remained normal (QT less than or equal to QS2). All the dynamic changes that occurred with acute standing tended to persist during prolonged amb-act.

Regulation of subcutaneous blood flow during head-up tilt (45 degrees) in normals

Local and remote regulation of subcutaneous blood flow in the forearm and leg was studied during head-up tilt (45 degrees) in 6 young healthy male subjects. Relative blood flow was estimated by the local 133Xe washout technique. Lowering of a leg to a 51% decrease in its subcutaneous blood flow due to a veno-arteriolar reflex elicited by the increase in venous transmural pressure. During head-up tilt subcutaneous blood flow in the arm remaining at heart level decreased by 27%, in the leg blood flow decreased by 50%. Following proximal nervous blockade, head-up tilt did not induce vasoconstriction in forearm at heart level, but blood flow in distal leg decreased by 45%. Thus there was no difference in the vasoconstrictor response in the leg to head-up tilt or lowering of the labelled area by 40 cm. Since head-up tilt caused neurogenically mediated vasoconstriction in subcutaneous tissue, subcutaneous blood flow in the extremities seems to be regulated by remote (baroreceptor) as well as local sympathetic reflex mechanisms (veno-arteriolar reflex).

Distinctive abnormal responses to tilting test in chronic Chagas' disease

The purpose of this study was to investigate the sympathetic nervous system function in 34 patients with chronic Chagas' disease. The tilting test was selected as an appropriate means to assess the adrenergic system function. Our results demonstrate that (a) all chagasics respond with a significantly smaller rise in diastolic blood pressure (0-3.8 mmHg) than normal subjects (9-12 mmHg), when submitted to the tilting test and (b) chagasic patients with heart failure have a significantly lower heart rate than normal subjects and nonchagasic heart failure patients (P < 0.05 and 0.001, respectively). With these results we may speculate that the damage in chronic Chagas' disease should be located in the sympathetic pathway. Therefore, the faulty orthostatic mechanism would be the consequence of a diminished adrenergic activity, with a defective arteriolar vasoconstriction and a decreased basal heart rate. At the same time we note that our results differ from the results of similar tests performed on the same kind of chagasic patients in Brazil, where a predominantly decreased parasymphathetic activity has been demonstrated.

The effect of upright tilt on the volume of the failing human left ventricle

The effect of a passive change from supine to 25-degree head-up tilted position on left ventricular volume was studied by echocardiography and other noninvasive techniques in 18 normal subjects, 6 patients with compensated LV volume overloading, and 12 patients with LV failure. In normal subjects and patients with compensated LV volume overloading, 10 minutes of head-up tilt resulted in a significant decrease in the echocardiographic LV internal dimension equivalent to a decrease in the calculated LV end-diastolic volume of 27 and 16 per cent, respectively. In contrast, no change in LV end-diastolic dimension and volume was noted during tilt in the patients with LV failure. The response of heart rate, blood pressure, and LV ejection fraction to this intervention was insignificant in all groups. These data indicate that volume preload is unresponsive to postural changes in patients with LV failure but not in normal subjects or in those with compensated LV volume overloading. It is suggested that the effect of posture on LV volume and output is primarily determined by the absence or presence of LV failure and the consequences of it on the peripheral circulation.

The effects of posture and isoproterenol on the velocity of left ventricular contraction in man. The reciprocal relationship between left ventricular volume and myocardial wall force during ejection on mean rate of circumferential shortening

A study was performed in five normal men in whom left ventricular volume was measured by thermodilution in the supine and 60 degrees head-up postures, in the control state, and then during steady-state response to isoproterenol. The mean rate of circumferential shortening of the left ventricle was calculated for each of the postures in both inotropic states and was found to remain constant in the control state at 12.5 +/-0.6 cm/sec in the supine posture and 13.3 +/-0.5 cm/sec in the tilted posture. Similarly, mean rate of circumferential shortening remained constant in response to the positive inotropic effect of isoproterenol at 20.9 +/-0.5 cm/sec in the supine position and 20.7 +/-0.5 cm/sec in the tilted posture. It is concluded that the constancy of mean rate of circumferential shortening over the relatively broad physiologic range of left ventricular end-diastolic volume and mean force of ejection during a given state of myocardial contractility represents the coupled reciprocal influences of ventricular wall tension and myocardial fiber length on the velocity of ventricular wall shortening. Unlike stroke work, stroke power, and mean rate of left ventricular ejection, which are volume-dependent parameters of myocardial performance, the mean rate of circumferential shortening appears to be a reasonable index of left ventricular contractility, which in steady-state conditions is independent of left ventricular end-diastolic volume and mean ventricular wall force of ejection. In this study, changes in mean rate of circumferential shortening associated with changes of heart rate were small and variable.

Left ventricular systolic time intervals as indices of postural circulatory stress in man

The effects of graded increments of passive head-up tilt on the duration of the systolic time intervals corrected for heart rate were investigated in 15 normal subjects. Head-up tilt caused a prolongation of the pre-ejection period and a shortening of the left ventricular ejection time, while total electromechanical systole diminished minimally. The lengthening of the pre-ejection period and abbreviation of the left ventricular ejection time increased progressively with stepwise increments of head-up tilt. The application of venous occlusive tourniquets produced changes in the systolic intervals directionally similar to those observed with head-up tilt. In contrast to the normal subjects, three patients with congestive heart failure demonstrated no change in the systolic time intervals during head-up tilt. After diuresis in two of the patients with heart failure, the responses of their systolic time intervals to head-up tilt returned toward normal.

Role of renin in acute postural homeostasis

Plasma renin activity has been measured by radioimmunoassay at frequent intervals after passive upright tilting and correlated with pulse and blood pressure in normotensive man. In the normal response to upright posture, renin activity in both peripheral and renal veins increases consistently within a few minutes. The renin rise lags behind the increase in pulse rate and diastolic blood pressure. Renin activity falls to base-line level soon after return to the horizontal position. In the 25% of normal subjects who develop vasovagal syncope after upright tilting, the increase in renin activity is smaller in magnitude and duration than in the normal response. Renin levels fall just before syncope appears and rise sharply after return to the horizontal position. Anephric patients are able to effect adequate postural adjustments even in the absence of renin activity.

This study indicates that the renin angiotensin system participates in the acute response to postural change in normal man and that it functions abnormally in vasovagal syncope.

Hemodynamic effects of hypovolemia in normal subjects and patients with congestive heart failure

Five young normal subjects (NS) and six middle-aged patients with chronic, low-output, congestive heart failure (HFP) were studied before and after 10 minutes of exposure to hypovolemia induced by negative pressure (30 mm Hg) applied to the lower body. ECG, respirometer, and catheters placed in the subclavian artery and superior vena cava permitted measurements of heart rate (HR), respiration rate, arterial and central venous pressures (CVP), and cardiac output (CO). In the group of NS, systemic vascular resistance (SVR) rose moderately, while CVP fell 4.3 mm Hg; CO, stroke volume (SV), stroke work (SW), and central blood volume (CBV) fell about 20%, whereas blood pressure and HR showed little change. In the group of HFP, control hemodynamic values were generally abnormal. In four patients the response to hypovolemia was similar to that of NS. Two patients with advanced heart failure showed no change or a rise in CO, SV, and SW in the face of a fall in CVP (3.1 and 3.7 mm Hg), no change or a fall in SVR, and a rise in CBV. It is concluded that HFP does not respond to hypovolemia in a consistent manner. Certain patients with advanced failure demonstrated abnormal responses to induced hypovolemia, the causes for which are complex.