Spectral analysis of systolic blood pressure and heart rate after heart transplantation in children

Enhanced exercise performance and survival associated with evidence of autonomic reinnervation in pediatric heart transplant recipients

Following heart transplantation (HTx), loss of autonomic input to the allograft results in elevated resting heart rate (HR) and decreased chronotropic reserve. As enhanced exercise capacity and HR recovery post exercise are suggestive of reinnervation in pediatric cohorts, we used heart rate variability (HRV) analysis to assess autonomic reinnervation in pediatric HTx recipients. Pediatric patients transplanted between 1996 and 2010 and with serial 24-hour Holter recordings post-HTx were analyzed for HRV using time and frequency domain measures. Of 112 patients, 68 (57%) showed evidence of autonomic reinnervation that was not associated with age at HTx. Evidence of reinnervation was associated with a significant increase in low-frequency power spectrum (p<0.001), suggesting sympathetic reinnervation. Patients with evidence of reinnervation showed higher percent-predicted maxVO(2) on performing an exercise test (+10.2 ± 3.6%, p = 0.006) and improved HR recovery at 3 minutes (-11.4 ± 3.9 bpm, p = 0.004), but no difference in percent-predicted maximal HR. Cox hazards modeling using presumed sinus reinnervation criteria at last Holter recording as a time-dependent covariate was associated with decreased hazard of mortality and/or retransplantation (HR: 0.2, 95% CI 0.04-1.0, p = 0.05). In conclusion, a majority of pediatric HTx recipients demonstrate evidence of reinnervation that is associated with functional outcomes. Studies to assess graft reinnervation as a marker of long-term prognosis are warranted.

Sympathetic control of short-term heart rate variability and its pharmacological modulation

The static relationship between heart rate (HR) and the activity of either vagal or sympathetic nerves is roughly linear within the physiological range of HR variations. The dynamic control of HR by autonomic nerves is characterized by a fixed time delay between the onset of changes in nerve activity and the onset of changes in HR. This delay is much longer for sympathetically than for vagally mediated changes in HR. In addition, the kinetics of the HR responses shows the properties of a low-pass filter with short (vagal) and long (sympathetic) time constants. These differences might be secondary to differences in nervous conduction times, width of synaptic cleft, kinetics of receptor activation and post-receptor events. Because of the accentuated low-pass filter characteristics of the HR response to sympathetic modulation, sympathetic influences are almost restricted to the very-low-frequency component of HR variability, but the chronotropic effects of vagal stimulation usually predominate over those of sympathetic stimulation in this frequency band. Oscillations in cardiac sympathetic nerve activity are not involved in respiratory sinus arrhythmia (high-frequency component) and make a minor contribution to HR oscillations of approximately 10-s period (low-frequency component of approximately 0.1 Hz), at least in the supine position. In the latter case, HR oscillations are derived mainly from a baroreflex, vagally mediated response to blood pressure Mayer waves. Beta-blockers and centrally acting sympathoinhibitory drugs share the ability to improve the baroreflex control of HR, possibly through vagal facilitation, which might be beneficial in several cardiovascular diseases.

Influences of a Relaxation Intervention on Perceived Stress and Power Spectral Analysis of Heart Rate Variability

This study was designed to determine whether power spectral analysis (PSA) of heart rate variability (HRV) can detect change in autonomic tone following a relaxation intervention called therapeutic touch (TT). Thirty healthy subjects underwent TT by one of three TT practitioners using the steps developed by Krieger and Kunz (The Therapeutic Touch, Prentice-Hall, 1979). Both subjects and TT practitioners were monitored by continuous electrocardiographic monitoring (Holter) before (15 minutes), during, and after (15 minutes) TT was administered. Subjects and TT practitioners completed a visual analogue scale (VAS) of perceived stress before and after TT. Change scores for VAS and PSA of high-frequency/low-frequency (HF/LF) ratios were compared for the 2-minute interval before TT began and the end of TT and the end of the recovery period, using t tests. VAS scores decreased (less stress) from before to after TT for both subjects (p < 0.0005) and TT practitioners (p < 0.0005). Mean HF/LF ratios increased significantly to reflect greater parasympathetic dominance from before TT to the end of treatment for subjects (p = 0.006), but not for TT practitioners. However, further analysis revealed that this change was due to an exaggerated HF/LF response from four outliers (p < 0.0005). Data collected in this study did not reveal differences between these four subjects and the rest of the sample. There were no significant changes in HF/LF ratios from the end of TT to end of recovery for either group. Further research is needed to determine why some subjects may have greater change in autonomic tone in response to relaxation in order to be able to predict who will demonstrate physiologic response to relaxation interventions.

Short-term testing of heart rate variability in heart-transplanted children: equal to 24-h ECG recordings?

INTRODUCTION

Heart rate variability (HRV) is reduced in adults and children after cardiac transplantation. Testing of HRV has been used to assess re-innervation of the cardiac graft; its reliability in ruling out acute graft rejection is still under investigation. This study used a short-term test on HRV in 23 heart and heart-lung transplanted children and adolescents and compared the results with 24-h ECG recordings.

PATIENTS AND METHODS

Twenty-three subjects (16.3+/-4.2 yr; 10 females) underwent a 10-min HRV test at two occasions and one 24-h ECG. HRV was calculated according to the time domain method (RR interval, standard deviation of RR interval) and the frequency domain method (total power, LF and HF for assessment of sympathovagal modulation of heart rate).

RESULTS

Correlation between the short-term tests and 24-h ECG was high with regard to the frequency domain analysis of HRV. Correlation was less pronounced in the time domain method.

CONCLUSIONS

In heart and heart-lung-transplanted children and adolescents, due to reduced overall HRV short-term testing may give as reliable data as 24-h ECG. Therefore, especially when power spectral analysis has to be performed as a longitudinal assessment of re-innervation of the cardiac graft, short-term testing may offer an easily applicable and non-invasive diagnostic tool. Further studies are warranted to investigate whether HRV testing may contribute to rule out acute graft rejection.

Reinnervation after heart transplantation in children: results of short-time heart rate variability testing

AIMS

To detect impairment in short-term heart rate variability (HRV) in children after heart and heart-lung transplantation (TX) as reported in adults. To assess vagal and sympathetic influence on the donor heart rate using frequency domain analysis of HRV.

METHODS AND RESULTS

Measurement of short-term HRV was performed in 17 patients (age 16.9+/-3.6, 6.1+/-3.7 yr after TX) and 12 healthy controls (age 14.8+/-3.0 yr). Testing consisted of a resting phase of 15 minutes followed by a tilt phase of 45 min. All HRV parameters were significantly impaired in transplanted patients: RR interval (RRI) 717.2+/-122.5 m/s (controls 827+/-139.7, p<0.05), standard deviation of RR interval (RRI-SD) 20.1+/-15.5 (89.9+/-38.4, p<0.001), RRI at tilt 607.9+/-79.7 (654.0+/-104.7, NS), RRI-SD at tilt 21.1+/-20.0 (60.4+/-31.4, p<0.001). Low-frequency (LF)/High-frequency (HF) ratio of HRV showed prominent sympathetic influence in TX-patients (3.38+/-5.60 vs. 1.18+/-0.86, NS) increasing during tilting (5.91+/-8.36 vs. 4.74+/-5.27, NS). In subgroup analysis, 4 yr after TX an increasing sympathetic control of heart rate was observed.

CONCLUSION

Short-term HRV is severely impaired in children after TX. If changes are observed, they are time-related and show increasing sympathetic influence starting from 4 yr after TX.

Parasympathetic versus sympathetic control of the cardiovascular system in young patients with type 1 diabetes mellitus

Autonomic neuropathy and cardiovascular dysregulation are common complications of the diabetes mellitus (DM). The aim of the study was to test the hypothesis that cardiovascular regulation is abnormal in young patients with type 1 DM. Patients with type 1 DM (17, 10 females, 7 males) aged 12.9-31.5 years (mean+/-SEM: 22.4+/-1.0 years) were investigated. The mean duration of DM was 12.4+/-1.2 years. The control group consisted of 17 healthy probands matched for sex and age. The length of R-R intervals was measured using telemetric system (VariaCardio TF4; Sima Media) where ECG signal (sampling frequency 1000 Hz) from thoracic belt was transferred into PC for further analysis. Systolic blood pressure (SBP) was monitored beat-to-beat using volume-clamp method by Finapres 2300 (Ohmeda). Spectral power in HF band of HRV (HRV-HF) was taken as an index of parasympathetic control and spectral power in LF band of systolic BPV (BPV-LF) as an index of sympathetic control. In young patients with type 1 DM significant reduction of spectral power in HF band of the heart rate variability was found, whereas no significant difference between DM group and control group was observed in spectral power in LF band of blood pressure variability. In conclusion, we found impaired parasympathetic control of heart rate in young patients with type 1 DM. No differences in blood vessels sympathetic control were detected using spectral analysis of BPV. We suggest that abnormalities in cardiac parasympathetic regulation precede impairment of blood vessels sympathetic control in young diabetics.

Hypertension in Heart and Heart-Lung Transplanted Children: Does Impaired Baroreceptor Function Play a Role?

BACKGROUND

Baroreceptor control of beat-to-beat blood pressure in heart and heart-lung-transplanted children is impaired. Time-related trends of baroreceptor function recovery are studied and a possible correlation of baroreflex impairment and systolic hypertension may give evidence for supplemental medical treatment of hypertension.

METHODS

Seventeen patients (six female) 6.1 +/- 3.7 years (range 0.8-13.0 years) after heart (n = 14) and heart-lung (n = 3) transplantation (TX) were studied. Twelve healthy children and 10 children after liver and bone marrow TX taking cyclosporine A (CyA) served as control groups 1 and 2, respectively. Baroreceptor sensitivity (BRS) was calculated from noninvasive systolic beat-to-beat blood pressure (sBP) measurement during a resting phase and a tilt-table test.

RESULTS

BRS was significantly impaired in the study group at rest and during tilting; mean sBP was slightly elevated. Significant difference between patients on CyA and healthy controls was not observed. Discrete recovery of BRS occurred after 4 years postTX with decreased sBP (n = 12 pts, BRS 6.78 +/- 7.44 msec/mmHg, sBP 116.2 +/- 12.4 mmHg) when compared to a postTX time course of less than 4 years (n = 5 pts, BRS 4.02 +/- 4.21 msec/mmHg, sBP 122.0 +/- 6.7 mmHg, P = NS).

CONCLUSION

BRS is disturbed after TX in children; four years postTX, a minimal recovery of BRS and a discrete reduction of sBP seem to occur. Those patients with a persistent low BRS and elevated sBP may profit from pharmacological influence in sympathovagal imbalance.

Effect of posture on heart rate variability spectral measures in children and young adults with heart disease

BACKGROUND

Reduction of heart rate variability as a consequence of heart disease and postural change has been well documented. However, the data on the effect of postural change in pediatric patients are incomplete and the effect is not fully understood. The aim of the study was to investigate effect of postural change on heart rate variability in relation to the extent of severity of heart disease.

METHODS

The dependence of heart rate variability on posture in 41 children and young adults (8-20 years) with heart disease has been investigated and compared with control. Short-term electrocardiograms (ECGs) were assessed in supine rest and active standing, and spectral measures of heart rate variability were determined.

RESULTS

Two types of response to the change of supine to standing posture were determined in both healthy and diseased subjects. In majority of subjects, the increased heart rate induced by standing was accompanied by a decrease in high-frequency power. However, in about 30% of all subjects, increased heart rate during standing was accompanied by an increased high-frequency power. Independently of posture and disease, high-frequency and low-frequency power were positively correlated. In subjects characterized by a reduction of heart rate variability in standing, the high-frequency power in both postures is reduced in diseased subjects compared to control.

CONCLUSIONS

These results demonstrate that in this age range, the response to posture is not unique because of the difference in high-frequency power, which implies a variety of vagal modulations of heart rate.

Evolution of heart rate control after transplantation: conduction versus autonomic innervation

In cardiac transplantation, the donor organ is not initially innervated and demonstrates decreased heart rate variability (HRV). However, HRV may improve after several months. The mechanism for HRV improvement has not been elucidated; autonomic "reinnervation" of the donor heart has been proposed. The role of atrioatrial conduction from recipient to donor organ has not been evaluated. We prospectively evaluated cardiac transplant patients with a limited electrophysiology study at the time of their surveillance biopsies. Recordings were made of recipient and donor signals, observing conduction properties between recipient and donor atria. Holter recordings were analyzed and HRV was determined using spectral analysis techniques, recording mean RR interval, low-frequency power (LF), high-frequency power (HF), and the LF/HF ratio. These were compared to published norms. From November 1999 to May 2000, 21 patients (6 female) who underwent cardiac transplantation participated at a median age of 101 months (range, 4.1-217 months). Time posttransplant ranged from 26 days to 71 months. Holter data were available for 20 patients and demonstrated dissociated P waves in 13 (65%). The mean heart rate on Holter was 111 beats per minute (bpm) (range, 85-161 bpm). We were able to record distinct recipient atrial signals in 16 of 21 (76%) patients. The average recipient tissue heart rate was 55% that of the donor heart rate. We documented atrioatrial association in only 1 patient. HRV did not reach normal values for most patients and did not increase with time posttransplantation. The LF values were in the normal range for most patients, whereas 3 patients had normal HF values and 2 patients had values just below normal. Recipients of heart transplantation have a predominantly sympathetic influence of HRV. These preliminary data suggest that atrioatrial conduction does not play a role in reestablishing normal heart rate control following pediatric cardiac transplantation.

Very high frequency oscillations in the heart rate and blood pressure of heart transplant patients

The authors studied the recently reported very high frequency (VHF) peaks in the heart rate (HR) and blood pressure (BP) power spectra of heart transplant (HT) patients. These VHF peaks appear at frequencies much higher than the respiratory frequency, in addition to the typical low-frequency and high-frequency peaks. Twenty-five recordings obtained from 13 male HT patients (0.5-65 months following surgery) were compared with recordings from 14 normal male subjects. The ECG, continuous BP and respiration were recorded during 45min of supine rest. Eight recordings from HT patients were excluded owing to arrhythmias. Spectral analysis was performed on all other recordings. VHF peaks were found in the spectra of both BP and HR in nine recordings obtained from six HT patients. In some cases, the power in the VHF peaks was markedly higher than that of the high-frequency peak. No VHF peaks were observed in eight recordings obtained from four HT patients or in recording from any of the normal subjects. No correlation was found between the incidence of VHF peaks and time after transplant. It was proved that the VHF peaks were not artifactual, and their significance within the framework of the theory of communication systems is discussed. The presence of those peaks was attributed to vagal denervation.

A common origin of the very low frequency heart rate and blood pressure variability--a new insight into an old debate

The purpose of this study was to assess the exact temporal and amplitude relationship between very low frequency heart rate variability waves and very low frequency blood pressure variability waves. We developed a computerized system based on a modified proportional-integral controller for the controlled increase of heart rate by isoproterenol. Heart rate and blood pressure were measured continuously in conscious tethered rats. Using time domain methods, we found that the very low frequency heart rate variability waves and the very low frequency blood pressure variability waves are irregular, while at the same time strikingly 1:1 synchronized with each other. In 78% of the cases, the phase between the peaks of the very low frequency heart rate variability waves and very low frequency blood pressure variability waves was negative (blood pressure leads). Their amplitudes were linearly related with a degree of hysteresis. As blood pressure went up, heart rate went down. Our results suggest with a high degree of probability that the very low frequency heart rate variability waves do not cause very low frequency blood pressure variability waves, and that these two signals are probably driven by the same autonomic nervous system controller/oscillator.

Morphology, distribution, and variability of the epicardiac neural ganglionated subplexuses in the human heart

Concomitant with the development of surgical treatment of cardiac arrythmias and management of myocardial ischemia, there is renewed interest in morphology of the intrinsic cardiac nervous system. In this study, we analyze the topography and structure of the human epicardiac neural plexus (ENP) as a system of seven ganglionated subplexuses. The morphology of the ENP was revealed by a histochemical method for acetylcholinesterase in whole hearts of 21 humans and examined by stereoscopic, contact, and bright-field microscopy. According to criteria established to distinguish ganglionated subplexuses, they are epicardiac extensions of mediastinal nerves entering the heart through discrete sites of the heart hilum and proceeding separately into regions of innervation by seven pathways, on the courses of which epicardiac ganglia, as wide ganglionated fields, are plentifully located. It was established that topography of epicardiac subplexuses was consistent from heart to heart. In general, the human right atrium was innervated by two subplexuses, the left atrium by three, the right ventricle by one, and the left ventricle by three subplexuses. The highest density of epicardiac ganglia was identified near the heart hilum, especially on the dorsal and dorsolateral surfaces of the left atrium, where up to 50% of all cardiac ganglia were located. The number of epicardiac ganglia identified for the human hearts in this study ranged from 706 up to 1,560 and was not correlated with age in most heart regions. The human heart contained on average 836 +/- 76 epicardiac ganglia. The structural organization of ganglia and nerves within subplexuses was observed to vary considerably from heart to heart and in relation to age. The number of neurons identified for any epicardiac ganglion was significantly fewer in aged human compared with infants. By estimating the number of neurons within epicardiac ganglia and relating this to the number of ganglia in the human epicardium, it was calculated that approximately 43,000 intrinsic neurons might be present in the ENP in adult hearts and 94,000 neurons in young hearts (fetuses, neonates, and children). In conclusion, this study demonstrates the total ENP in humans using staining for acetylcholinesterase, and provides a morphological framework for an understanding of how intrinsic ganglia and nerves are structurally organized within the human heart.

Short-term variability of pulse pressure and systolic and diastolic time in heart transplant recipients

In heart transplant recipients (HTR), short-term systolic blood pressure variability is preserved, whereas heart rate variability is almost abolished. Heart period is the sum of left ventricular ejection time (LVET) and diastolic time (DT). In the present time-domain prospective study, we tested the hypothesis that short-term fluctuations in aortic pulse pressure (PP) in HTR were related to fluctuations in LVET. Seventeen male HTR (age 48 +/- 6 yr) were studied 16 +/- 11 mo after transplantation. Aortic root pressure was obtained over a 15-s period using a micromanometer both at rest (n = 17) and following the cold pressor test (CPT, n = 14). There was a strong positive linear relationship between beat-to-beat LVET and beat-to-beat PP in all patients at rest and in 13 of 14 patients following CPT (each P < 0.01). The slope of this relationship showed little scatter both at rest (0.34 +/- 0.07 mmHg/ms) and following CPT (0.35 +/- 0.09 mmHg/ms, P = not significant). Given the essentially fixed heart period, DT varied inversely with LVET. As a result, in 13 of 17 HTR at rest and in 12 of 14 HTR following CPT, there was a negative linear relationship between beat-to-beat PP and DT. In conclusion, our short-term time-domain study demonstrated a strong positive linear relationship between LVET and blood pressure variability in male HTR. We also identified a subgroup of HTR in whom there was a mismatch between PP and DT.

Assessment of short-term blood pressure variability in anesthetized children: a comparative study between intraarterial and finger blood pressure

OBJECTIVE

Continuous blood pressure (BP) measurement provides instantaneous information on hemodynamic status, and allows for assessment of sympathetic modulation of vasomotor tone using spectral analysis. As an alternative to intraarterial blood pressure (IABP) measurement, the Finapres, a photoplethysmographic device, allows for non-invasive continuous measurement of finger blood pressure (FBP). This study was designed to evaluate the accuracy of spectral measurements of FBP variability in children during anesthesia and recovery. For this purpose, reliability of BP measurement and short-term BP variability assessed by FBP were calculated and compared with IABP.

METHODS

Finger blood pressure was compared with IABP from the ipsilateral radial artery, in 14 children undergoing major surgery. Sixty-seven simultaneous recordings of both signals were performed during anesthesia and 32 during recovery period. The accuracy of the FBP was determined by measuring its bias and precision according to the Bland and Altman method. To assess the ability of the FBP to follow short term BP variability, bias of total spectral power and bias of the 3 main spectral components (LF, MF, HF) were calculated. Transfer functions between invasive and non-invasive signals were calculated.

RESULTS

The average bias of SBP measurement was 3.8 +/- 7.4 mmHg during anesthesia and 2.2 +/- 6.7 mmHg during recovery. During anesthesia overall variability and spectral components of FBP and IABP were similar with both techniques; while during recovery, a selective amplification of the low frequencies (< 0.15 Hz) of FBP was observed. Frequency response analysis of the pressure waveform, showed a high coherence between both signal with a gain of 0.96 +/- 0.52 mmHg FBP/ mmHg IABP under anesthesia, and of 0.74 mmHg FBP/ mmHg IABP during recovery.

CONCLUSIONS

The differences evidenced between FBP and IABP spectral profiles might result from specific physiological properties of digital arteries, which are sympathetic effectors. This study supports the use of FBP in children to assess non-invasively the vascular sympathetic component of the autonomic nervous system during anesthesia and recovery.

Influence of type of surgery on the occurrence of parasympathetic reinnervation after cardiac transplantation

BACKGROUND

Cardiac autonomic reinnervation after human cardiac transplantation has been demonstrated frequently but to date only for sympathetic efferents. Standard surgical techniques leave many parasympathetic branches intact in the original atria and thus with less stimulus to reinnervate the donor atria.

METHODS AND RESULTS

We used changes in the RR-interval power spectrum induced by sinusoidal modulation of arterial baroreceptors by neck suction at different frequencies to detect both parasympathetic and sympathetic reinnervation in 79 subjects with "standard" and 10 "bicaval" heart transplants. In 24 subjects (17 standard and 7 bicaval), the protocol was repeated 6 and 11 months after transplantation. Neck suction at 0.20 Hz produced a component at 0.20 Hz in the RR-interval spectrum not due to respiration (fixed at 0.25 Hz), which suggested parasympathetic reinnervation, in 4 of 10 bicaval but in only 2 of 79 standard transplant subjects (whose recipient atria underwent >50% resection to remove scars of previous interventions), P<.001. In only 1 (bicaval) transplant subject was parasympathetic reinnervation present 6 months after transplantation (confirmed 3 months later); in 4 subjects, it was absent at 6 months but appeared after 11 months after transplantation. Atropine (0.04 mg/kg i.v.) abolished the response to fast (0.20 Hz) and reduced that to slow stimulation, confirming the presence of parasympathetic reinnervation (4 subjects).

CONCLUSIONS

Parasympathetic reinnervation depends on the surgical technique: because bicaval surgery cuts all sympathetic and parasympathetic nerves, regeneration might be stimulated similarly in both branches. Standard surgery cuts only approximately 50% of sympathetic fibers; most recipient parasympathetic axons remain intact, hence their regeneration might not be stimulated.

Spectrum analysis of cardiovascular time series

The demand for noninvasive assessment of cardiovascular control parameters has promoted the use of spectrum analysis. These techniques have been applied on a broad basis; however, because of the abstract mathematical approach, spectrum analysis in physiology is still not fully accepted by some circles in the scientific community. Thus it is the goal of the following review to focus on the rationale for applying spectrum analysis in different fields of circulation research, which range from determining arterial baroreceptor reflex sensitivity to the early detection of heart allograft rejection. Within this scope, major findings regarding the physiological and pathophysiological regulation of the cardiovascular system are discussed. In addition, inherent limitations of these methods are made clear. Toward the end of this survey, a perspective is provided for the general readership.

Does low-frequency variability of heart period reflect a specific parasympathetic mechanism?

Low frequency (LF, approximately 0.1 Hz) spontaneous oscillations of heart period in humans have been attributed to and correlated with the sympathetic efferent control of the heart. However, this interpretation is controversial, because sympathetic blockade does not suppress these oscillations, while parasympathetic blockade strongly affects them. The sympathetic origin of LF of arterial pressure, on the contrary, has been convincingly demonstrated. Four 10 min cycle-by-cycle time series of R-R interval (RR), and systolic (SAP) and diastolic (DAP) arterial pressure were produced by automatic analysis of data obtained with non-invasive methods in 10 healthy humans during supine rest and while standing, both before and after beta 1-selective blockade (atenolol). Time series were analysed by autoregressive transfer function analysis. beta-blockade failed to induce systematic changes on the power of the LF peak of RR, in any condition. The coherence between RR and SAP in the same region remained high (0.77 +/- 0.03) and a constantly negative phase (approximately 50-60 degrees, corresponding to a delay of 1-2 heart beats of RR on SAP) was always seen. beta-blockade decreased the power of the LF peak of SAP, increased the transfer function gain between SAP and RR at LF, and the HF power of RR. We conclude that LF oscillations of RR are not directly generated by the sympathetic drive to the heart but reflect mainly the parasympathetic activity. The results suggest that the LF oscillations of the vagal outflow, and of RR, are generated by the baroreceptor reflex, driven by sympathetically-induced blood pressure LF waves.

Circadian variations of blood pressure and heart rate early and late after heart transplantation

Cardiac reinnervation late after heart transplantation has been reported in individual patients. As a measure for reinnervation, circadian changes in arterial blood pressure and heart rate have been used but not yet systemically evaluated in cardiac transplant recipients. Ambulatory blood pressure and heart rate monitoring was performed in 62 patients for 24 hr early (<6 months, mean 26 days, range 5-90 days, n=30) and late (> or = 6 months, mean 12 months, range 7-78 months, n=32) after heart transplantation. A loss of physiological nocturnal decline in blood pressure and heart rate was noted early after transplantation, whereas late after operation an improvement in circadian changes of blood pressure and heart rate was observed. The patients late after heart transplantation had a significant higher diastolic blood pressure. A pathological circadian blood pressure and heart rate pattern was observed in patients early after heart transplantation, which was improved late after operation. This could be explained by partial reinnervation of the heart. Diastolic hypertension late after transplantation may be due to cyclosporine treatment and/or neuroendocrine hyperactivity.