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PubMed1983

[Development of the maximal dipole moment of the heart with respect to postnatal heart growth].

The maximal dipole moment of the heart of various species shows a proportionality to the heart weight. The present study investigates whether this relation is also valid for the postnatal period. The Nelson-lead-system separates the influence of the heart growth from that of the body growth. It allows to calculate the resultant dipole moment of the heart. Our experiments were applied to guinea pigs. The postnatal increase of the body weight and heart weight and the development of the dipole moment were obtained for the first 25 d of life. The results show a linear increase of the body weight with age. In contrast, the resultant dipole moment of the heart is almost constant during the first 14 d of life. Only after the 2nd week of life, the maximal dipole moment increases with further age. Evidently, during the first 14 d of the postnatal development other important factors than the growing heart mass influence the magnitude of the dipole moment.

Age Factors↗

PubMedDate not supplied

Epstein-Barr virus infection in heart and heart-lung transplant recipients: incidence and clinical impact.

BACKGROUND: A retrospective serologic study was made of 67 heart-lung and 295 heart transplant recipients (with transplantations at Papworth Hospital, Cambridge, England) to determine the incidence and clinical impact of Epstein-Barr virus infection. METHODS: Epstein-Barr virus capsid antigen immunofluorescence tests were performed, and the antibody avidity was determined by modifying the washing procedure to include a mild reducing agent (8M urea). RESULTS: This testing showed that 6.0% of the patients had primary Epstein-Barr virus infections, whereas 17.4% had the reactivation of a past infection. Primary infections were only detected in patients who were Epstein-Barr virus antibody-negative before transplantation, who had received an organ from an Epstein-Barr virus antibody-positive donor. Of the patients with serologically proven Epstein-Barr virus infections, 52.9% had symptoms. Although these were generally mild, five heart and two heart-lung transplant recipients had malignant lymphoma and one heart and one heart-lung transplant recipient had lymphoproliferative disease after Epstein-Barr virus infection. Additional four heart transplant recipients had lymphoma after transplantation. None of these four patients had evidence of active Epstein-Barr virus infection; one was Epstein-Barr virus antibody-negative during the study period and three had stable Epstein-Barr virus virus capsid antigen immunoglobulin G titers throughout. CONCLUSIONS: Epstein-Barr virus infection in organ transplant recipients may lead on to life-threatening lymphoproliferative disease or lymphoma. For this reason it may be beneficial to monitor patients after transplantation for evidence of Epstein-Barr virus infection and to follow the progress of those affected.

Adolescent↗

PubMedDate not supplied

HLA mismatching and outcome in heart, heart-lung, and single lung transplantation.

BACKGROUND: To determine the influence of HLA mismatching on rejection after cardiothoracic organ transplantation, we analyzed results in 243 recipients. METHODS: There were 183 heart, 25 heart-lung, and 35 single lung recipients, all receiving triple-drug immunosuppression with anti-thymocyte globulin induction. Zero, one, and two mismatches occurred by chance at each locus in between 0% to 9%, 26% to 35%, and 47% to 70% of recipients, respectively. RESULTS: In heart recipients, compared with a two mismatch, a zero mismatch was associated with a lower linearized rejection rate in the first 6 months. A zero B locus mismatch was likewise associated with less rejection in month 1, and DR zero mismatch with reduced rejection in the first 3 months. Steroid withdrawal was more successful in those with zero mismatch at any locus. In heart-lung recipients linearized rejection was significantly lower in those with lesser degrees of A and DR locus mismatching, and after single-lung transplantation linearized rejection was significantly lower with lesser degrees of A and B locus mismatching from 3 to 6 months only. Actuarial survival did not differ for any organ with any degree of mismatch at any locus. CONCLUSIONS: HLA mismatching affects rejection, but the effect is limited to the early postoperative period for heart and heart-lung recipients. Lower grades of mismatch increase the likelihood of successful steroid withdrawal for heart recipients. The chance occurrence of no mismatch at any locus is rare, making prospective matching infeasible. HLA mismatching identifies patients at higher risk of rejection. The best use of this information may be to guide early immunosuppression, limiting prospective matching to retransplants or with presensitized recipients.

Graft Rejection↗

PubMedDate not supplied

Circadian rhythm changes in blood pressure and heart rate during the first year after heart transplantation.

Heart transplant recipients (n = 11) were studied before discharge from the hospital and 1, 3, 6, and 12 months after transplantation to (1) examine systolic and diastolic blood pressure and heart rate circadian patterns, (2) detect the presence or absence of nocturnal declines, and (3) describe changes in the mean levels of systolic blood pressure, diastolic blood pressure, and heart rate. An ambulatory blood pressure-monitoring system was used to record blood pressure and heart rate at 1-hour intervals for up to 48 hours. Data were analyzed with descriptive and independent t-test statistics, as well as cosinor analysis for rhythmicity. The majority of the patients had significant (p < 0.05) circadian rhythms for systolic and diastolic blood pressure and heart rate throughout the study, but at times the systolic and diastolic blood pressure acrophases were found to be phase shifted to earlier or later along the time axis (e.g., peak values occurring at 3 AM rather than later in the morning or early afternoon), such that no relationships were found between circadian rhythms and nocturnal declines. More "normal" circadian rhythms were observed for heart rate than for systolic and diastolic blood pressures. The development of hypertension (systolic/diastolic blood pressures > 140/90 mm Hg) was common and by 6 months and 1 year after transplantation 8 of the 10 patients remaining in the study were hypertensive. Increases in mean heart rate of approximately 18% (ranging from 2% to 46%) were also observed during the first postoperative year.

Blood Pressure↗

PubMed1993

Tissue typing, heart and heart-lung transplantation.

The effects of HLA matching and the presence of pre-existing anti-HLA antibodies, together with cross-match results, on heart and heart-lung transplants are discussed. Prospective HLA matching of donor and recipient is not usually performed for heart and heart-lung transplants. In a multi-centre study statistically significant improved survival with the better-matched heart grafts was found. In a small series of heart grafts it was also found that the improvement with HLA matching was confined to male recipients who were not blood group O. Heart graft recipients with wide panel reactive antibody had worse graft survival one year after transplant than the unsensitized. In several studies patients with a positive cross-match had a significantly lower survival rate than those with a negative cross-match. It is suggested that, minimally, pre-transplant screening and prospective cross-matching of highly sensitised patients is necessary.

ABO Blood-Group System↗

PubMedDate not supplied

Heart transplantation techniques in complex congenital heart disease.

Of 207 pediatric patients who underwent orthotopic heart transplantation at Loma Linda University Medical Center through January 1993, 96% of infants under 6 months of age and 45% of older infants and children had complex structural heart disease. Twelve patients had visceral heterotaxia, 10 had isolated dextrocardia, and 16 had unusual atrial situs, including five with situs inversus. Therefore a prerequisite for successful heart transplantation in early life is a surgical team skilled in the management of congenital heart disease. Transplantation in very early life is usually primary therapy, whereas in older infants and children it is an exercise in reoperative and reconstructive heart surgery. The keys to operative success include the following: (1) Appropriate recipient selection; (2) en bloc recovery of all veins and arteries required for anatomic reconstruction; (3) adequate myocardial protection; and (4) use of low-flow hypothermic perfusion and intermittent circulatory arrest as required. Although there is wide variability in the anatomic presentation of many potential recipients with congenital heart disease, only two absolute anatomic contraindications have been identified. Absence or marked hypoplasia of central pulmonary arteries and absence or markedly diminutive pulmonary veins are two anatomic variants that do not yield to heart transplantation therapy. Previous palliative surgery, variations of atrial situs, anomalies of pulmonary or systemic venous connections, and great vessel malformations all create challenge for the surgical team and potential risk for the recipient, but none preclude operative success.

Child↗

PubMedDate not supplied

Mode of death in patients with congestive heart failure: comparison between possible candidates for heart transplantation and patients with less advanced disease.

To study whether the relative incidence of sudden death versus progressive congestive heart failure is related to the severity of congestive heart failure as assessed by determination of peak oxygen consumption, we followed 90 ambulatory patients with moderate to severe congestive heart failure for 24.1 +/- 13.1 months. All patients had a left ventricular ejection fraction of 40% or less (mean, 22.6% +/- 9.2%) and a peak oxygen consumption of 20 ml/min/kg or less (mean, 14.7 +/- 3.5 ml/min/kg). Patients with severe congestive heart failure who might be eligible for heart transplantation (group I: n = 37; peak oxygen consumption < or = 14 ml/min/kg, mean, 11.0 +/- 1.8 ml/min/kg; mean left ventricular ejection fraction, 22.3% +/- 9.3%) were compared with those considered too well for heart transplantation (group II: n = 53; peak oxygen consumption > 14 < or = 20 ml/min/kg, mean, 17.1 +/- 1.6 ml/min/kg; mean left ventricular ejection fraction, 22.9% +/- 9.1%). During follow-up, 15 patients (41%) in group I died; 11 patients (21%) in group II died. In group I, seven of the 15 deaths (47%) were sudden; in group II, nine of the 11 deaths (82%) occurred suddenly. Patients who died suddenly had a significantly higher peak oxygen consumption (14.0 +/- 3.5 ml/min/kg) than those who died of progressive congestive heart failure (11.0 +/- 3.1 ml/min/kg; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Death, Sudden↗

PubMed1993

[Heart failure in valvular heart disease].

The clinical manifestations of heart failure depend importantly on the rate at which the syndrome develops and specifically on whether sufficient time has elapsed for compensatory mechanisms to become operative and for fluid to accumulate in the interstitial space. In most cases of the valvular heart diseases, patients survive the acute insult, and anatomical and functional abnormalities of the valves develop gradually, so that a host of compensatory mechanisms develop, especially cardiac hypertrophy. These allow the patient to adjust to and tolerate not only the anatomical abnormalities, but also a reduction in cardiac output or changes in loading condition, with less difficulties. The most important goal of treatment for the patients with chronic heart failure is to improve prognosis and the quality of life. Surgical correction is one of the best way to obtain good results in the treatment of the valvular heart diseases. We have been evaluated left ventricular pump function and contractile function before and after surgery for valvular diseases using the method for estimating myocardial contractility, that is, the relationship between ejection fraction and end-systolic volume or a ratio of end-systolic wall stress to end-systolic volume (ESS/ESVI), estimated the reversibility of the left ventricular systolic function after surgery, and determined the timing of operation. To make precise evaluation for the heart failure in patients with chronic valvular heart diseases, particularly during compensatory period, reduced pump function and myocardial contractility rather than clinical symptoms should be assessed and considered as an indicator for severity of the heart failure.

Aortic Valve Insufficiency↗

PubMed1998

Morbidity, functional status, and immunosuppressive therapy after heart transplantation: an analysis of the joint International Society for Heart and Lung Transplantation/United Network for Organ Sharing Thoracic Registry.

BACKGROUND: The morbidity and mortality studies on heart transplantation to date have come from single-center or multicenter studies that often have required collection of data over periods of time greater than a year. Data are now available from the International Society for Heart and Lung Transplantation/United Network for Organ Sharing (ISHLT/UNOS) Thoracic Registry from all centers in the United States performing heart transplantation, which allows analysis of morbidity and mortality rates on an annual basis. METHODS: All transplantation centers in the United States are now required to submit registration (at the time of transplantation) and 1-year follow-up clinical data on all heart transplant recipients to the ISHLT/UNOS Thoracic Registry. Data forms were submitted to the Registry regarding pretransplantation diagnoses, causes of death, rehospitalization, functional and work status at 1 year, immunosuppressive therapy, and the development of complications such as hypertension, hyperlipidemia, renal insufficiency, diabetes, and malignancy. This study is an analysis of this database for the period of April 1, 1994, through March 31, 1995, examining specifically morbidity, functional status, and other clinical events occurring during the period after the initial hospitalization and up to the first-year follow-up. The study cohort consisted of the 1853 patients who survived the initial hospitalization and for whom matching registration and 1-year follow-up forms were available. RESULTS: Rehospitalization during the first year after the initial admission was required by more than 40% of survivors, and at least one third of these required admission to the intensive care unit. Infection and rejection were the most common reasons for rehospitalization, each accounting for about 20%. Complications during the first year occurring in 10% or more of survivors included hypertension, diabetes, renal dysfunction, and hyperlipidemia. Less common complications included symptomatic bone disease, chronic liver disease, cataracts, stroke, and malignancy. Allograft function was excellent among survivors at 1 year, with a mean ejection fraction of 57.4% and less than 7% of patients requiring pacemaker therapy or having development of coronary artery disease. Eighty-three percent of survivors reported no functional limitations, but only 27% were working full-time. Eighty-nine percent of survivors were receiving prednisone at their 1-year follow-up. CONCLUSION: Clinical data are now available from the ISHLT/UNOS Thoracic Registry on the basis of the initial registration and 1-year follow-up of all patients undergoing heart transplantation in the United States. Analysis of these data from April 1, 1994, through March 31, 1995, demonstrates that the first year after the initial hospitalization for heart transplantation is a period of significant morbidity and frequent rehospitalization but excellent survival. In spite of a high level of functional capacity at 1-year follow-up, only a minority of patients return to work. The ISHLT/UNOS Thoracic Registry can now serve as a valid source of data for future analysis of trends in heart transplantation in the United States.

Activities of Daily Living↗

PubMedDate not supplied

Heart rate variability in the human transplanted heart: nonlinear dynamics and QT vs RR-QT alterations during exercise suggest a return of neurocardiac regulation in long-term recovery.

RATIONALE: Functional reinnervation of the transplanted human heart by the autonomic nervous system has not been demonstrated. A lack of autonomic control of the transplanted allograft is reflected by an increased resting heart rate, a sluggish heart rate response to dynamical exercise and a reduced heart rate variability. Recent evidence suggests that a measure of deterministic chaos in the heartbeat interval series (point correlation dimension, PD2i) is superior to the conventional power spectrum or other stochastic measures in detecting changes in the mechanism underlying heartbeat generation. METHODS: The PD2i is based on the presumption that the variability is determined and patterned, whereas the stochastic measures all assume that the variability is around a stationary mean and is noise. The PD2i reconstructs the degrees of freedom (number of independent variables) in the system that generates the time series examined, and does this irrespective of whether the system is stochastic or deterministic and is stationary in time. RESULTS: PD2i was determined for heartbeat intervals (RR, ECG digitized at 1200 Hz; supine posture) of 23 heart transplant recipients (HTR: 9 adults, 14 children; 0.04-7.7 years after transplantation) and 21 healthy control subjects (CTL; 13 adults, 8 children). The PD2i (+/-SD) averaged 5.4 +/- 0.7 for the CTL adults and 5.4 +/- 0.6 for the CTL children. Mean PD2i was reduced after transplantation to 1.1 +/- 0.1 in 6 HTRs recorded within 1 year after surgery; in one HTR recorded 2 weeks after surgery the mean PD2i was 3.7. Between 1 to 2 years PD2i was found increased in 2 of 3 subjects and between 2 to 8 years it was increased in 13 of 13, but not to control levels. In normal hearts the QT subinterval of each heartbeat cycle is associated with inotropy and the RR-QT remainder with chronotropy (i.e., the dyastolic interval during which RR is primarily regulated). To examine more closely the residual and returning heartbeat dynamics of the HTR subjects, these subinterval series were examined during mild exercise (40 to 90 Watts) and its recovery. In recent HTRs, resting QT and RR-QT were moderately reduced and modulated by exercise and recovery, but with an approximate 100 beat latency. In long-term (7-8 years) HTR subjects there was a rapid and larger response to exercise/recovery, but compared to normal the range was smaller and the complexity of the subinterval trajectories in time was simpler. CONCLUSIONS: Recurrence of low-dimensional deterministic dynamics after transplantation suggests recovery of neurocardiac control attributable to 1) reorganization of the viable intrinsic cardiac nervous system, 2) reinnervation by the extrinsic autonomic nervous system, or 3) both.

Adult↗

PubMed1979

Echocardiography and fetal heart sounds in the diagnosis of fetal heart block.

A 32-week fetus was demonstrated phonocardiographically and echocardiographically to have a regular atrial rate of 150 per minute and a regular ventricular rate of 39 per minute, indicating complete heart block. The diagnosis was suspected when two groups of heart sounds at two distinct rates were heard on auscultation, and was confirmed by the postnatal ECG. The maternal history was significant for the presence of systemic lupus erythematosus. The basis for the echocardiographic diatnosis of complete heart block, the presence of atrial heart sounds in complete heart block, and the relationship of maternal SLE to congenital heart block are discussed.

Adult↗

PubMed1989

Is the adaptation of right ventricular refractoriness to an abrupt increase in heart rate impaired in chronic heart failure?

Chronic heart failure is associated with a high risk of ventricular arrhythmias and sudden death, although the mechanisms leading to these arrhythmias are not fully understood. To determine if the adaptation of ventricular refractoriness to an abrupt increase in heart rate is impaired in heart failure, electrophysiologic findings in 11 patients with structurally normal hearts (group I) were compared to findings in 28 patients with chronic heart failure (mean left ventricular ejection fraction 0.23 +/- 0.05). Heart failure was due to coronary artery disease in 14 patients (group II) and to idiopathic dilated cardiomyopathy in 14 patients (group III). The effective refractory period at the right ventricular apex was measured during unipolar cathodal pacing at twice diastolic threshold following a 12-beat ventricular drive at a cycle length of 600 msec. The pacing cycle length was then decreased to 400 msec for one, two, and three beats and the refractory period was determined for each beat at the faster rate. For each beat the mean refractory periods of group II and III patients were similar and were significantly longer than those of group I patients (p less than 0.01). The refractory period progressively shortened at the 400 msec cycle length and the percent decrease for each beat was similar among all three groups (p greater than 0.10). In the group II and III patients there was no correlation of the refractory period or change in refractory period with the pulmonary artery, right atrial, and pulmonary capillary wedge pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

Frequency spectra of the first heart sound and of the aortic component of the second heart sound in patients with degenerated porcine bioprosthetic valves.

To determine the usefulness of the frequency of heart sounds in the assessment of porcine bioprosthetic valve degeneration, frequency spectra of phonocardiograms of the first heart sound and the aortic component of the second sound were analyzed in 31 patients with degenerated porcine bioprosthetic valves. Comparisons were made with 35 control patients whose valves were inserted 1 month or less. Among 23 patients with degenerated porcine bioprosthetic valves in the mitral position, the dominant frequency of the first heart sound was 95 +/- 11 Hz, which exceeded the first sound in 18 controls (51 +/- 3 Hz) (p less than 0.01). The degenerated mitral porcine bioprosthetic valves of 14 patients showed calcification or fibrosis and the first heart sound in these patients was 115 +/- 16 Hz, which exceeded that of control subjects (p less than 0.001). The degenerated mitral porcine bioprosthetic valves of 9 patients showed torn leaflets only, and the first heart sound in these patients was 64 +/- 9 Hz, which did not differ from that of control subjects. In the aortic position, 8 valves were degenerated and the aortic component of the second sound was 109 +/- 12 Hz, which was higher than that in 17 control subjects (63 +/- 4 Hz) (p less than 0.001). Only 2 of these degenerated valves showed tears unaccompanied by calcific deposits or fibrosis, and the frequencies were comparable to that of control subjects. These observations indicate that the frequency of heart sounds in patients with degenerated porcine bioprosthetic valves becomes abnormally elevated when degeneration is accompanied by calcification or fibrosis, which causes the cusps to stiffen.

Aortic Valve↗

PubMed1998

[The prognostic value of heart rate variety on congestive heart failure of pregnant women].

OBJECTIVE: To explore the prognostic value of heart rate variety (HRV) on congestive heart failure (CHF) of pregnant women complicated with organic heart disease. METHOD: One hour ambulatary electrocardiography was performed in 61 pregnant women complicated with organic heart dieases at about the 28th-32th week in gestational period and 7 days after delivery respectively. RESULT: 9 patients occured CHF later, their HRV time domain index were significantly decreased (P < 0.001, P < 0.05), compared with patients without CHF as control group. 7 days after delivery, When the condition of CHF patients was improved. Their SD, SD SD value increased. CONCLUSION: HRV has some value of assessing the cardiac reserve and predicting the happen of Congestive Heart Failure in pregnant women complicated with organic heart disease.

Adult↗

PubMed2002

Pathophysiological characterization of isolated diastolic heart failure in comparison to systolic heart failure.

CONTEXT: Many older patients with symptoms of congestive heart failure have a preserved left ventricular ejection fraction (LVEF). However, the pathophysiology of this disorder, presumptively termed diastolic heart failure (DHF), is not well characterized and it is unknown whether it represents true heart failure. OBJECTIVE: To assess the 4 key pathophysiological domains that characterize classic heart failure by systematically performing measurements in older patients with presumed DHF and comparing these results with those from age-matched healthy volunteers and patients with classic systolic heart failure (SHF). DESIGN AND SETTING: Observational clinical investigation conducted in 1998 in a general community and teaching hospital in Winston-Salem, NC. PARTICIPANTS: A total of 147 subjects aged at least 60 years. Fifty-nine had isolated DHF defined as clinically presumed heart failure, LVEF of at least 50%, and no evidence of significant coronary, valvular, or pulmonary disease. Sixty had typical SHF (LVEF < or =35%). Twenty-eight were age-matched healthy volunteer controls. MAIN OUTCOME MEASURES: Left ventricular structure and function, exercise capacity, neuroendocrine function, and quality of life. RESULTS: By echocardiography, mean (SE) LVEF was 60% (2%) in patients with DHF vs 31% (2%) in those with SHF and 54% (2%) in controls. Mean (SE) LV mass-volume ratio was markedly increased in patients with DHF (2.12 [0.14] g/mL) vs those with SHF (1.22 [0.14] g/mL) (P<.001) and vs controls (1.49 [0.17] g/mL) (P =.002). Peak oxygen consumption by expired gas analysis during cycle ergometry was similar in the DHF and SHF groups (14.2 [0.5] and 13.1 [0.5] mL/kg per minute, respectively; P =.40) and in both was markedly reduced compared with healthy controls (19.9 [0.7] mL/kg per minute) (P =.001 for both). Ventilatory anaerobic threshold was similar in the DHF and SHF groups (9.1 [0.3] and 8.7 [0.3] mL/kg per minute, respectively; P<.001) and in both was reduced compared with healthy controls (11.5 [0.4] mL/kg per minute) (P<.001). Norepinephrine levels were similar in the DHF (306 [64] pg/mL) and SHF (287 [62] pg/mL) groups (P =.56) and in both were markedly increased vs healthy controls (169 [80] pg/mL) (P =.007 and.03, respectively). Brain natriuretic peptide was substantially increased in both the DHF (56 [30] pg/mL) and the SHF (154 [28] pg/mL) groups compared with healthy controls (3 [38] pg/mL) (P =.02 and.001, respectively). Quality-of-life decrement score as assessed by the Minnesota Living with Heart Failure Questionnaire was substantially increased from the benchmark score of 10 in both groups (SHF: 43.8 [3.9]; DHF: 24.8 [4.4]). CONCLUSION: Patients with isolated DHF have similar though not as severe pathophysiologic characteristics compared with patients with typical SHF, including severely reduced exercise capacity, neuroendocrine activation, and impaired quality of life.

Aged↗

PubMed1998

31P-NMR analysis of congestive heart failure in the SHHF/Mcc-facp rat heart.

31P-NMR was used to monitor myocardial bioenergetics in compensated and failing SHHF/MCC-fa(cp) (SHF) rat hearts. The SHHF/Mcc-fa(cp) (spontaneous hypertension and heart failure) rat is a relatively new genetic model in which all individuals spontaneously develop congestive heart failure, most during the second year of life. Failing SHF rat hearts displayed a pronounced decrease in resting PCr:ATP ratios (P<0.001), which was explained by a significant (P<0. 0001) drop in total creatine (47.2+/-3.1 nmol/mg protein) v age matched controls (106+/-3 nmol/mg protein). In end stage failure, NMR determined PCr was 2.9+/-0.1 micro mol/g wet weight under basal conditions. In contrast, 6- and 20-month-old controls and compensated SHFs had PCr values of 5.3+/-0.1, and 5.1+/-0.5 and 5. 1+/-0.2 micro mol/g wet weight. Both compensated and failing SHF hearts were metabolically compromised when the rate pressure product (RPP) was increased, as evidenced by an increase in Pi and a drop in PCr. Compensated SHF hearts, however, were able to increase rate pressure products (RRP, mmHg X beats/min) from 44.5+/-1.4 to 66.6+/-3. 4 K with dobutamine infusion, whereas hearts in end-stage failure were able to increase their RPP from baseline values of 27+/-4 K to only 37+/-7 K. The data indicate that a pronounced decline in PCr and total creatine signals the transition from compensatory hypertrophy to decompensation and failure in the SHF rat model of hypertensive cardiomyopathy.

Adenine Nucleotides↗

PubMed1994

Differences in pulse rate and heart rate and effects on the calculation of heart rate reactivity during periods of mental stress.

Heart rate and reactivity from pulse and ECG were compared over rest and mental arithmetic periods of 2-min duration each for 32 males and 50 females. Data from the two sources of heart rate were not significantly different during the rest period but did differ significantly during periods of heart rate acceleration and deceleration. Sex effects were also noted, with females having consistently higher heart rates from both sources of measurement. Calculation of heart rate reactivity via five procedures based upon the wider literature revealed significant differences between data from different sources of heart rate. Implications for assessment of heart rate reactivity to laboratory stressors are discussed, with suggestions for future research.

Adolescent↗

PubMed1987

Heart-lung interaction: effect on regional lung air content and total heart volume.

To study the interactions between and within the heart and lungs, end-diastolic (ED) and end-systolic (ES) volumes and intrathoracic location of the heart, and the regional air content, volume and geometry of the lungs, were measured from three-dimensional image data generated with the Dynamic Spatial Reconstructor (DSR). The DSR was used to scan the full thoracic extent of anesthetized dogs and sloths at selected transpulmonary pressures. The results show that the dependent to nondependent gradient of regional lung opacity (or conversely regional air content) in the supine animal was not present in the prone animals. While the rib cage and diaphragm of the dog deformed markedly, the shape of the sloth's rib cage and diaphragm remained essentially constant with change in body orientation. As a consequence of these findings, we deduce that the observed change in gradient of regional lung air content in both dog and sloth are in response to changes in the intrathoracic position of the heart which alter ventral lung geometry and not a response to changes in rib cage or diaphragm geometry. In a second series of studies we reconstructed the 3-D extent of the heart at ED and ES in supine anesthetized dogs and demonstrated that the total heart volume (THV) (i.e. contained by the pericardial sac) during sinus rhythm differs by less than 5% between ED and ES. The DSR image data show that this is achieved by the epicardial apex remaining essentially fixed and that the plane containing the atrio-ventricular valves moves like a plunger towards the apex in systole. When atrial fibrillation is present, the THV no longer remains constant and decreases during systole, presumably because of increased stiffness of the atrial myocardium. We conclude from the experimental results that the heart plays an important role in determining regional differences in alveolar expansion, and that by maintaining a constant THV, the heart minimizes energy expenditure which would be caused by moving the lung.

Animals↗