Level and diurnal variations of hormones of interest to the cardiovascular system in patients with heart transplants

Comparison of office, home, and ambulatory blood pressure in heart transplant recipients

BACKGROUND

The purpose of this study was to prospectively evaluate the relationship between office, home, and ambulatory blood pressure (BP) in heart transplant recipients.

METHODS AND RESULTS

The study enrolled 30 adults ≥ 6 months after heart transplantation. Morning seated office BP was measured with the use of an automatic device at 3 outpatient visits. Seated home BP was measured in the morning and evening for 5 consecutive days. Ambulatory BP was measured over 24 hours with the use of a Spacelabs monitor. The strongest correlation was observed between home and 24-hour ambulatory BP (r = 0.79 systolic; r = 0.72 diastolic). Office and home systolic BPs were significantly lower than daytime ambulatory BP (office, -3.7 mm Hg, P = .009; home, -2.6 mm Hg, P = .05). Ambulatory monitoring identified more participants with BP above hypertensive limits than did office or home measurements (63%, 50%, and 13%, respectively; P = .003). Ambulatory monitoring also revealed high BP loads, abnormal nocturnal BP patterns (eg, 30% nondippers), and a high percentage of masked hypertension (37% home, 50% ambulatory).

CONCLUSIONS

Office and home BP monitoring are acceptable but may underestimate BP burden in heart transplant recipients. Additional studies are needed to determine which BP method is superior for the management of hypertension and associated outcomes after heart transplantation.

Circadian variation of blood pressure: the basis for the chronotherapy of hypertension

Ambulatory blood pressure (BP) measurements present a close correlation with target organ damage and cardiovascular events, including myocardial infarction, stroke and cardiovascular mortality. With the use of this measurement technique, a significant circadian variation has been shown to characterize BP. This circadian BP variation, although affected by a variety of external factors, represents the influence of internal factors such as ethnicity, gender, autonomic nervous system tone, vasoactive hormones, and hematologic and renal variables. In most individuals, BP presents a morning increase, a small post-prandial valley, and a deeper descent during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced or even reversed. This cannot be determined by traditional clinical or home BP assessments. Subjects with a diminished nocturnal BP decline (non-dipper pattern) have a significantly worse prognosis than the ones with a normal dipper pattern. In particular, the non-dipper circadian BP pattern represents a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia and myocardial infarction. The normalization of the circadian BP pattern to a dipper profile is a novel therapeutic goal, and accumulating medical evidence suggests this can delay the progression towards the renal and cardiovascular pathology known to be a consequence of the non-dipper BP pattern. The features of the circadian BP profile have direct implications for improving the drug-delivery of antihypertensive therapies as well as the qualification of patients for medication trials and assessment.

Blood Pressure After Cardiac Transplantation in Childhood

BACKGROUND

There has been little formal study of blood pressure in children after cardiac transplantation.

METHODS

Twenty-four-hour and clinical blood pressure (BP) were measured in 28 children (>6 months after transplantation) and compared with a large amount of normal data.

RESULTS

Conventional (clinical) systolic BP (SBP) was elevated in 9 (32.1%) of 28 (95% confidence interval [CI] 15.8 to 52.3), and conventional diastolic BP (DBP) was elevated in 5 (17.8%) of 28 (95% CI 6.0 to 36.8). Mean 24-hour BP was >97.5 percentile in 2 (7.7%) of 26 (95% CI 0.9 to 25.1) for SBP and in 7 (28.0%) of 25 (95% CI 12.1 to 49.4) for DBP. In comparison with the control population, mean nighttime SBP was 8.9 mm Hg higher in the transplanted group (95% CI 4.8 to 13.1), but daytime and mean 24-hour SBP were similar. Mean day, night, and 24-hour DBP was significantly higher in the transplanted patients. The nighttime decrease in BP was significantly less than controls for SBP, but not for DBP. Conventional BP measurement was poorly predictive of 24-hour BP. There was a significant association between mean 24-hour SBP and interventricular septal thickness (r(2)=0.35; p=0.01). DBP was not associated with interventricular septal thickness (r(2)=0.07; p=0.20) but was significantly correlated with the time since transplantation (r=0.42; p=0.03 for conventional DBP and r=0.43; p=0.04 for 24-hour DBP).

CONCLUSIONS

The elevation of DBP in children after cardiac transplantation is unexplained. The elevation in nighttime SBP has possible important therapeutic implications and is not predicted by conventional (clinical) BP measurement.

Nocturnal enuresis is a common complication following cardiac transplantation

AIMS

To investigate the incidence of nocturnal enuresis post-cardiac transplantation.

METHODS

Seventy two cardiac transplantations have been performed in children under 16 years of age. All recipients who were alive and over 4 years of age at the time of the study received a questionnaire about urinary symptoms; 54 of the 57 eligible children participated.

RESULTS

Twenty five children had persistent nocturnal enuresis post-transplantation. Thirteen of them had previously attained reliable night-time dryness but developed secondary nocturnal enuresis following transplantation, with three subsequently regaining dryness at ages 8, 12, and 17 years; 10 were still wetting mean age 12.3. Twelve children had not achieved night-time dryness when transplanted (all were under 4 years of age at the time) and continued to wet. Only one of these children achieved dryness (at age 12 using oxybutynin); the other 11 remained wet at night at a mean age of 9.3 years. Twenty nine children were dry at night post-transplantation, but 21 of them had nocturia at least three times a week. There is a significant difference in age at transplantation between the primary nocturnal enuretic children (mean age 2.0) and the secondary nocturnal enuretic children (mean age 7.4) as well as between the primary nocturnal enuretic children and the non-enuretic children (mean age 9.0).

CONCLUSIONS

Transplanting young children frequently delays the normal attainment of night-time continence or causes them to start wetting again. It should not be dismissed as a minor problem as it causes low self-esteem and is socially limiting. It is important families are aware it is a direct result of the transplantation process.

Cyclosporin effect on noradrenaline release from the sympathetic nervous endings of rat aorta

Arterial hypertension is one of the main side effects of cyclosporin treatment and seems to be due to activation of the sympathetic nervous system. Some authors hypothesized that cyclosporin may act on the sympathetic nervous endings increasing catecholamine release, in agreement with our previous works which demonstrated an increase in rat plasma catecholamine levels after 30 mg/kg per day cyclosporin treatment for 7 weeks. Therefore, the aim of this work was to study the cyclosporin mechanism responsible for that increase in plasma catecholamines. Male Wistar rats were used. Noradrenaline release was performed in vitro experiments after loading rat aorta abdominal segments with 3H-noradrenaline (3H-NA). The release of 3H-NA was measured after electrical stimulation in the presence of 10(-6)M cyclosporin. In another set of experiments electrical stimulation was replaced by a pulse addition of cyclosporin (10(-6)M). Another group of rats was treated with 30 mg/kg per day cyclosporin for 7 weeks and catecholamine contents in aorta abdominal segments and adrenals were measured by high performance liquid chromatography system with electrochemical detection (HPLC-ECD). An increase in the 3H-NA release was observed in both types of in vitro experiments. Since cocaine abolished these cyclosporin effects, the obtained results suggest that cyclosporin may act on the catecholamine transporter across the membrane. In addition, after the 7 weeks of cyclosporin treatment, a significant decrease in catecholamine aorta contents was verified but in adrenals there was no difference regarding to controls. However, the dopamine synthesis/degradation ratio measured by the DA/DOPAC ratio suggests an increase in dopamine synthesis. These facts are in agreement with the enhanced plasma catecholamine levels and with the hypothesis of tissue catecholamine depletion. However, they do not explain the increase in plasma adrenaline levels, since adrenaline is a reflex of adrenal activity. The synthesized dopamine in adrenals seems to be unable to reach vesicles and to be metabolized in adrenaline. The observed decrease in HVA adrenal levels may be a consequence of extraneuronal uptake inhibition or inhibition by cyclosporin of the direct o-methylation of DOPAC. In conclusion, our results suggest that cyclosporin increases catecholamine release from the sympathetic nervous endings by a tyramine-like effect, i.e. by acting directly on the catecholamine transporter of the membrane.

Sequential big endothelin plasma levels in heart transplant recipients during bridging therapy and after successful heart transplantation

BACKGROUND

The purpose of this study was to investigate the impact of successful heart transplantation in patients with refractory heart failure receiving bridging therapy on sequential plasma levels of big endothelin, norepinephrine, atrial natriuretic peptide and aldosterone.

METHODS

Fourteen patients (2 women, 12 men) accepted for heart transplantation were studied. All had severe chronic heart failure refractory to optimized oral therapy with angiotensin-converting enzyme inhibitors and furosemide, were in New York Heart Association functional Class IV, and had a left ventricular ejection fraction of <15%, Right heart catheterization was performed in all patients (cardiac index 1.9 +/- 0.1 liters/min. m(2), pulmonary capillary wedge pressure 30 +/- 2 mmHg, systemic vascular resistance index 2,827 +/- 253 dyn. s/cm(5). m(2)). As bridging therapy, patients received either prostaglandin E(1), prostaglandin E(1) and dobutamine or dobutamine alone as a continuous infusion. Neurohumoral variables were measured prior to bridging therapy and 3.5 months before and 7 and 10 months after successful heart transplantation.

RESULTS

Big endothelin, norepinephrine and atrial natriuretic peptide plasma levels decreased from 7.4 +/- 2.9 fmol/ml, 1112 +/- 686 pg/ml and 366 +/- 312 pg/ml to 6.0 +/- 4.5 fmol/ml, 720 +/- 503 pg/ml and 198 +/- 160 pg/ml, respectively, after bridging therapy, and further to 2.1 +/- 0.9 fmol/ml (p < 0.00001 vs baseline), 527 +/- 31 pg/ml (p < 0.02 vs baseline) and 115 +/- 70 pg/ml (p < 0.03 vs baseline), respectively, after cardiac transplantation. Aldosterone plasma levels decreased from 242 +/- 220 pg/ml to 183 +/- 142 pg/ml during bridging therapy and increased after heart transplantation to 252 +/- 189 pg/ml. Plasma creatinine levels increased from 1.2 +/- 0.4 mg/dl at baseline to 1.4 +/- 0.2 mg/dl after transplantation (NS).

CONCLUSIONS

The study suggests that excessive overproduction of big endothelin, atrial natriuretic peptide and norepinephrine is predominantly related to pump failure and, after cardiac transplantation, a moderate spillover of big endothelin persists. Its specific origin, however, remains to be elucidated. Furthermore, our data suggest a protective effect of prostaglandin E(1) on kidney function after heart transplantation.

Beneficial hemodynamic and renal effects of intravenous enalaprilat following coronary artery bypass surgery complicated by left ventricular dysfunction

OBJECTIVE

Angiotensin-converting enzyme inhibitors are an effective therapy for all stages of heart failure due to reduced systolic left ventricular function. Because sufficient data on intravenous angiotensin-converting enzyme inhibitors following coronary artery bypass surgery complicated by postoperative left ventricular dysfunction are unavailable, the efficacy and safety of intravenously administered enalaprilat were evaluated.

DESIGN

A placebo-controlled, randomized, double-blind protocol.

SETTING

Postoperative intensive care unit at the German Heart Institute Berlin.

PATIENTS

Forty patients with a left ventricular ejection fraction <35% following coronary artery bypass surgery on the second postoperative day or after weaning from intra-aortic balloon counterpulsation.

INTERVENTIONS

A loading dose of enalaprilat 0.625 mg infused over 1 hr was followed by 5 mg/24 hrs administered continuously for up to 72 hrs.

MEASUREMENTS AND MAIN RESULTS

Systemic and pulmonary hemodynamic variables, blood gases, hormonal variables, renal function, and electrolytes were measured before and repeatedly during therapy. Acute effects were as follows: At 1 hr, enalaprilat increased the cardiac index (p <.001), stroke volume index (p <.001), and right ventricular stroke work index (p <.03) compared with placebo, whereas mean arterial pressure (p <.008) and both systemic (p <.001) and pulmonary (p <.02) vascular resistance decreased. Continuous effects were as follows: Over 72 hrs, enalaprilat decreased diastolic pulmonary artery pressure (p <.019), pulmonary artery occlusion pressure (p <.02), and central venous pressure (p <.02). The cardiac and stroke volume indexes were consistently higher in the enalaprilat group, whereas systemic and pulmonary vascular resistances were lower. The arterial blood-pressure lowering effect was blunted and heart rate remained unchanged. Mixed venous oxygenation (p <.02) was higher and arterial oxygenation was not modified. Finally, enalaprilat increased creatinine clearance (p <.002) and decreased creatinine (p <.02) and urea (p <.03).

CONCLUSIONS

Intravenous enalaprilat safely and effectively improves cardiac and renal function following coronary artery bypass surgery complicated by postoperative left ventricular dysfunction.

Plasma N-terminal proatrial natriuretic factor can predict normal pulmonary capillary wedge pressure in cardiac transplant recipients

BACKGROUND

Plasma N-terminal proatrial natriuretic factor (proANP) is closely related to atrial filling pressure, but this may be distorted in heart transplant recipients.

OBJECTIVE

The aim of this study was to examine the usefulness of proANP as a non-invasive marker of cardiac filling pressure in transplanted patients with normal to moderately elevated serum creatinine (s-creatinine).

METHODS

Blood was sampled at rest for analysis of proANP from 220 patients 1-13 (median 4) years after orthotopic heart transplantation undergoing routine diagnostic catheterization.

RESULTS

In multivariate analysis proANP was significantly positively related to s-creatinine, mean pulmonary capillary wedge pressure (PCWP) and time after transplantation and negatively related to haemoglobin and cardiac index. All the patients with proANP below 1140 pmol/l had normal PCWP (<13 mmHg). The area under the receiver-operating characteristic curve for proANP for the detection of PCWP > 13 mmHg was 0.81. The positive predictive value of proANP for detection of increased PCWP was very low.

CONCLUSION

A low proANP had a 100% negative predictive value for increased atrial pressure but the low positive predictive value makes proANP unsuitable as an indicator of increased atrial pressures in heart transplanted patients.

The loss of circadian heart rate variations in patients undergoing mitral valve replacement and Corridor procedure--comparison to heart transplant patients

We have presently demonstrated that when added to mitral valve replacement (MVR) the corridor procedure is 75% efficient in restoring and maintaining sinus rhythm in patients with chronic atrial fibrillation (AF), caused by rheumatic mitral valve disease, (follow up 13.9months). In the same patient population, we observed that the typical day-night cycle heart rate (HR) variations were lost and our present study concentrates on this subject. Heart rate variability analysis based on 24-h Holter ECG recording (StrataScan 563 DelMar Avionics) or hospital discharge (12th-14th postoperative days) was performed in 3 patient groups: Group I: Patients with a Corridor procedure added to MVR (12pts, m/f 10/2, mean age 47.3+/-7.5yr); Group II (control): with patients MVR performed through the left atrial approach, without additional antiarrhythmic procedures (10pts, m/f 3/7 mean age 51.5+/-6.7yr), and Group III: heart transplant recipients (5pts, mean age 46.4+/-11.22yr). We analyzed the hourly heart rate over 24-h period divided into three 8-h segments (07-14h; 15-22h and 23-06h). Statistical comparison of mean hourly heart rate values was made between the three time periods of Holter monitoring. The Corridor procedure performed with mitral valve replacement resulted in conversion of sinus rhythm in 75% of patients (Group I), but postoperative heart rate variability analyses based on Holter monitoring disclosed that the mean heart rate was not statistically significantly difficult between the three 8-h segments of the day-night (P>0.05). The same results were found in the group of patients after heart transplant (P>0.05). The same results were found in the group of patients after heart transplant (P>0.05). In the second group (classical MVR), statistically significant differences in mean HR variation existed between the three 8-h intervals (P<0.05), and although atrial fibrillation occurred postoperatively physiologic circadian heart rate variations were preserved. With the Corridor procedure, both atria were surgically and electrically isolated and chronotropic function of the ventricles was restored by creating a small strip of atrial tissue with isolated sinus node and atrio-ventricular node, connected to the ventricles. This technique produced heart denervation nervous system influence, producing the loss of circadian HR variations, similar to the transplanted heart.

Enhanced natriuretic response to neutral endopeptidase inhibition in heart-transplant recipients

Heart-transplant recipients (Htx) generally present with body fluid and sodium handling abnormalities and hypertension. To investigate whether neutral endopeptidase inhibition (NEP-I) increases endogenous atrial natriuretic peptide (ANP) and enhances natriuresis and diuresis after heart transplantation, ecadotril was given orally to 8 control subjects and 8 matched Htx, and levels of volume-regulating hormones and renal water, electrolyte, and cyclic guanosine monophosphate (cGMP) excretions were monitored for 210 minutes. Baseline plasma ANP, brain natriuretic peptide (BNP), and cGMP were elevated in Htx, but renin and aldosterone, like urinary parameters, did not differ between groups. NEP-I increased plasma ANP (Htx, 20.6+/-2.3 to 33.2+/-5.9 pmol/L, P<0.01; controls, 7.7+/-1. 2 to 10.6+/-2.6 pmol/L) and cGMP, but not BNP. Renin decreased similarly in both groups, whereas aldosterone decreased significantly only in Htx. Enhanced urinary sodium (1650+/-370% versus 450+/-150%, P=0.01), cGMP, and water excretions were observed in Htx and urinary cGMP positively correlated with natriuresis in 6 of the Htx subjects. Consistent with a normal circadian rhythm of blood pressure, without excluding a possible effect of NEP-I, mean systemic blood pressure increased similarly in both groups at the end of the study (6.9+/-2.0% versus 7.4+/-2.8% in controls and Htx). Thus, systemic hypertension, mild renal impairment, and raised plasma ANP levels are possible contributory factors in the enhanced natriuresis and diuresis with NEP-I in Htx. These results support a physiological role for the cardiac hormone after heart transplantation and suggest that long-term studies may be useful to determine the potential of NEP-I in the treatment of sodium retention and water retention after heart transplantation.

Neurohumoral cardiovascular responses to alcohol and their modulation by peroral fluid

Reports on the physiologic effects of acute alcohol are far from uniform and probably reflect differences in study designs, which seldom or never consider the effects of coadministered volumes. We therefore measured blood pressure, heart rate, and heart rate variability (HRV) by power spectrum analysis, baroreceptor sensitivity, arterial blood flow, pulsed-wave velocity (PWV), and plasma levels of vasoactive hormones according to 2 protocols: group A = alcohol, 1 g/kg body weight, mixed with 500 ml of juice; and group B = similar to A plus 750 ml of mineral water. Each group comprised 9 healthy men, studied before and during the subsequent 1 and 1/2 hours after finishing the alcohol. In A, but not in B, alcohol increased heart rate (p = 0.01) and lowered systolic pressure (p <0.05). Plasma renin activity decreased only in B (p <0.01). Atrial natriuretic factor decreased in A, but increased in B (both p <0.02). Pancreatic polypeptide decreased (both p <0.001), and catecholamines did not change. In both groups, alcohol reduced PWV and increased blood flow. Baroreceptor sensitivity and the high-frequency band of HRV decreased in both groups. The physiologic response to acute administration of alcohol appears to depend on the volume of coadministered volumes. Alcohol further appears to interfere with vagal, rather than with sympathetic activity.

Natriuresis after cardiopulmonary bypass: relationship to urodilatin, atrial natriuretic factor, antidiuretic hormone, and aldosterone

OBJECTIVE

Recent studies suggest that urodilatin from the kidneys rather than atrial natriuretic factor from the heart is the more important member of the family of natriuretic peptides involved in the normal regulation of renal sodium and water excretion. We thus examined the relationship between natriuresis, urodilatin, and atrial natriuretic factor in patients after cardiopulmonary bypass, a procedure known to increase levels of atrial natriuretic factor significantly.

METHODS

Excretion rates of sodium and water were correlated with the excretion of urodilatin and with circulating levels of atrial natriuretic factor, antidiuretic hormone, aldosterone, and plasma renin activity during a period of 16 hours in 12 patients having had coronary artery bypass operations and with approximately a 400% elevation in levels of atrial natriuretic factor.

RESULTS

Natriuresis did not correlate with atrial natriuretic factor, antidiuretic hormone, aldosterone, or plasma renin activity. Excretion rates of urodilatin, however, correlated significantly with excretion rates of sodium (r = 0.74, p = 0.03), urine flow (r = 0.83, p = 0.01), and with levels of serum sodium (r = 0.82, p = 0.01).

CONCLUSION

These results suggest an important role for urodilatin, greater than that of atrial natriuretic factor, in the regulation of renal excretion of sodium and water after cardiopulmonary bypass surgery.

Diurnal changes in cyclosporine effect on ornithine decarboxylase and noradrenergic and cholinergic activities in submaxillary lymph nodes

Diurnal changes in cyclosporine efficacy to affect ornithine decarboxylase activity, [3H]norepinephrine uptake and [3H]choline conversion into [3H]acetylcholine were examined in rat submaxillary lymph nodes. Cyclosporine (5 or 20 mg/kg) caused a dose-dependent decrease in lymph node ornithine decarboxylase, being active at 5 or 20 mg/kg in Freund's adjuvant-treated rats, and at 20 mg/kg in rats treated with the adjuvant's vehicle. In immunized rats the lower cyclosporine dose was ineffective when injected during the night. Cyclosporine increased lymph node [3H]norepinephrine uptake dose dependently, with significant differences between the 20 mg/kg dose and controls in vehicle-treated rats and between 5 or 20 mg/kg and controls in Freund's adjuvant-treated rats. In immunized rats, 5 mg/kg cyclosporine increased [3H]norepinephrine uptake when injected at 13:00 or 17:00 h. Both doses of cyclosporine augmented lymph node synthesis of [3H]acetylcholine to a similar extent. In immunized and non-immunized rats cyclosporine suppressed the diurnal rhythm of lymph node adrenergic and cholinergic activity found in controls. After unilateral sympathetic denervation (by superior cervical ganglionectomy) and/or unilateral parasympathetic decentralization (by chorda tympani section), cyclosporine (5 mg/kg) decreased Freund's adjuvant-induced activation of lymph node ornithine decarboxylase when injected at 17:00 or 01:00 h. On the sham-operated side, cyclosporine was effective when injected at 17:00 h only. Decentralization, or a combined ganglionectomy plus decentralization, decreased lymph node ornithine decarboxylase activity. The results active regulation of the effects of cyclosporine in submaxillary lymph nodes by local autonomic nerves.

Ambulatory blood pressure monitoring. Application to clinical medicine and antihypertension medication trials

The wide use of ABPM has resulted in greater appreciation of the circadian time structure of BP variability and its clinical relevance. It is now recognized that the day-night change in BP results from an interplay of circadian rhythms in neurohumoral mechanisms coupled with temporal patterns in physical activity and mental load. The composite effect and balance of these endogenous and exogenous cyclic phenomena give rise to elevated BP during diurnal activity and reduced BP during nighttime repose in both normotension and uncomplicated essential hypertension. The balance is frequently disturbed in complicated and secondary forms of hypertension causing gross alteration of the 24-hour BP profile. ABPM also reveals the efficiency of antihypertensive treatment throughout the 24 hours and as a function of drug administration time. The pharmacokinetics and/or pharmacodynamics of antihypertensive medications have been demonstrated to vary with ingestion time. Such time-dependencies arise from circadian rhythms in BP and underlying mechanisms. The effect of antihypertensive medications is not simply superimposed upon endogenous bioperiodicities. Rhythms in neurohumoral mechanisms of BP control may modulate treatment effect. Certain aspects of the shape of the 24-hour BP profile, such as the magnitude of the morning surge and nocturnal decrease, have been implicated as determinants of morbid and mortal cardiovascular events. One large clinical multicenter investigation, known as the CONVINCE (Controlled Onset Verapamil Investigation of Clinical Endpoints) trial, is aimed at assessing the impact (cardiovascular morbidity and mortality) of verapamil chronotherapy over standard diuretic or beta anatagonist treatment in hypertensive patients with at least one risk factor of coronary heart disease. ABPM will help ascertain to what extent depression of the morning surge in BP relates to reduction in cardiac morbidity and mortality in this as well as other such trials. In any event, the importance of ABPM and the indices derived from its application are just beginning to be appreciated and explored.

Abnormal diurnal variation of blood pressure, cardiac output, and vascular resistance in cardiac transplant recipients

BACKGROUND

An attenuated or absent nocturnal decline in blood pressure has repeatedly been documented in cardiac transplant recipients. The present study was aimed at investigating the hemodynamic mechanism underlying this abnormality.

METHODS AND RESULTS

In 23 cardiac transplant recipients (11 to 36 months after transplantation) and in 23 control subjects matched for age and 24-hour mean arterial pressure, invasive 24-hour ambulatory blood pressure was measured by means of the Oxford technique. Beat-to-beat relative values of stroke volume were determined by means of a pulse-contour method, and relative changes of cardiac output (stroke volume x heart rate) and total peripheral vascular resistance (blood pressure/cardiac output) over the 24-hour period were calculated. The nocturnal decline in blood pressure was 20 +/- 8% (mean +/- SD) in control subjects but only 5 +/- 9% (P < .001) in cardiac transplant recipients. In control subjects, the nocturnal decline in blood pressure was associated with a nocturnal fall in cardiac output of 24 +/- 13%, whereas vascular resistance compared with daytime value did not change. The small nocturnal decline in blood pressure in cardiac transplant recipients was associated with an attenuated nocturnal fall in cardiac output of 14 +/- 12% (P < .05 versus control subjects). In addition, vascular resistance compared with daytime value was increased by 9 +/- 9% (P < .05) during the night. Both in cardiac transplant recipients and in control subjects, the nocturnal changes in blood pressure were correlated with the nocturnal changes in cardiac output but not with the nocturnal changes in total peripheral vascular resistance.

CONCLUSIONS

This study confirms the attenuated nocturnal fall in blood pressure in cardiac transplant recipients. Hemodynamically, this attenuated blood pressure decline is characterized by a reduced nocturnal fall in cardiac output, and it is associated with a nocturnal increase in vascular resistance.

Diurnal variation in blood pressure in patients with biventricular assist devices and retained, nonpumping native hearts

BACKGROUND

Studies indicate that centrally mediated rhythms in sympathetic tone play a prominent role in diurnal cardiovascular variability. Recent evidence from heart transplant recipients, in whom blood pressure does not decline during sleep despite normal variability in plasma norepinephrine, however, suggests that afferent cardiac nervous traffic is necessary for the generation of diurnal variability. This implies that in the presence of an innervated heart excluded from the systemic circulation, blood pressure would still decrease during sleep. To assess this hypothesis, we studied 24-hour blood pressure, heart rate, and neuroendocrine variability in patients with biventricular assist devices in whom the retained native hearts had ceased to pump.

METHODS AND RESULTS

Eight patients were free of medication and were studied every 3 hours. Pump rates and output were kept constant throughout the study. Blood pressure showed a significant decline during sleep, as did norepinephrine and epinephrine (all P < .05). Atrial natriuretic factor showed a significant increase around midnight (P < .01). Significantly elevated levels were found for all hormones studied except for aldosterone and endothelin.

CONCLUSIONS

Our results suggest that diurnal variations in cardiac function or in catecholamine levels (indicative of sympathetic activity) as found in cardiac transplant recipients alone are not responsible or sufficient for producing a nocturnal drop in blood pressure. The presence of an innervated heart appears crucial in this respect. This could be of importance for the understanding of circadian cardiovascular pathophysiology.

Lack of circadian rhythm of plasma concentrations of vasoactive intestinal peptide in patients with orthotopic heart transplants

OBJECTIVE

To study the circadian pattern of plasma concentrations of vasoactive intestinal peptide (VIP) in patients with orthotopic heart transplants. Circulating VIP is known to have neural and immunological sources.

PATIENTS AND METHODS

13 patients with orthotopic heart transplants were studied 12-53 months (mean 31.8 months) after operation. All were haemodynamically compensated and had no histological evidence of rejection. They were being treated with cyclosporin, azathioprine, and prednisone. Ten healthy individuals were studied as controls. Circulating VIP was assayed six times within a 24h period. Time qualified data were analysed by ANOVA and the cosinor method. Student's t test for unpaired data and Bingham's test for cosinor-derived parameters were used for statistical comparisons.

RESULTS

Plasma concentrations of VIP were lower in the patients with orthotopic heart transplants than in the controls (p < 0.001). ANOVA and the cosinor method respectively showed a statistically significant within-day variability and circadian rhythm in the controls but not in the patients with heart transplants.

DISCUSSION

The low plasma concentrations of VIP in the patients with heart transplants could be the result of the lack of contribution by the cardiac VIPergic fibres, a reduction of VIP release by the pharmacologically suppressed immune system, the inhibitory effects of cyclosporin on neural function and humoral secretions, and the effects of negative feedback on VIP release of high concentrations of atrial natriuretic peptide. The lack of the circadian rhythm suggests a structural disorder, which should be further investigated.