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Biomedical subjects

B J Rubal

Publications and source records attributed to B J Rubal.

18 recordsLinked to original sources
PubMed1991

Effects of respiration on size and function of the athletic heart.

This study compares the effects of quiet breathing on the heart structure and function of pentathlon athletes (n = 11) and a less-conditioned control group (n = 12). Two-dimensional echocardiography was employed to direct an M-mode beam through the heart to minimize measurement errors due to respiratory motion of the heart. Respiration was simultaneously recorded with M-mode echocardiograms from a minimum of five respiratory and an average of 25 cardiac cycles. Athletes had greater (p less than 0.01) end-diastolic transverse dimensions (10%), and interventricular septal and left ventricular posterior wall thicknesses (25%). During inspiration right ventricular internal end-diastolic dimensions increased (8 vs 12%) and left ventricular end-diastolic dimension (LVIDd) decreased (7 vs 8%) in athletes and controls, respectively. Although significant reciprocal changes in LVIDd (p less than 0.01) occurred during respiration, no respiratory change was noted in the transverse diameter of the heart, interventricular septal, posterior wall thickness, LV end-systolic volume or ejection fraction. Inspiration caused a 21% fall (p less than 0.01) in LV stroke volume in both groups. Eighty-four to 92% of the inspiratory decrease in LV stroke volume in the subjects studied could be attributed to ventricular interdependence; no significant interaction was found between level of conditioning and respiration.

Echocardiography↗
PubMed1990

Isolated aorta setup for hemodynamic studies.

A setup consisting of a high-performance hydraulic pump connected to the ascending part of an isolated aorta, including all major distal branches, each loaded with calibrated artificial resistors, was developed. The system was used to study total aortic compliance of the baboon as a function of mean aortic pressure (n = 5). The aorta loaded with the resistors was mounted in a custom-designed sink table, such that it was submersed in physiological saline maintained at 37 degrees C. Mean distending pressure in the entire aorta could be varied. The three-element Windkessel model was used to estimate total aortic compliance from pressure and flow waves generated by the pump. Total aortic compliance as a function of mean pressure was fitted with a logarithmic function: Ln(Compliance) = A + B * P. The value of A (+/- SE) was: 1.565 +/- 0.319 and B: -0.020 +/- 0.003 (P less than 0.001). The results were compared with previously published results (also using the same three-element Windkessel fit) obtained in three of the same animals in vivo. The in vivo data were A: 1.095 +/- 0.235 and B: B: -0.019 +/- 0.003. In vitro data had a significantly higher value of A than in vivo (P = 0.017), implying a significantly higher aortic compliance in vitro than in vivo. Occlusion of the proximal descending aorta was performed at a low distending pressure (55 mm Hg) to determine the proximal compliance. It was found (n = 4) that 46 +/- 11% (SD) of the total arterial compliance is to be attributed to the ascending and proximal descending aorta.

Animals↗
PubMed1989

Comparison of the frequency response characteristics of catheter-mounted piezoelectric and micromanometric phonotransducers.

This study compares the frequency response characteristics of catheter-mounted piezoelectric sound transducers with micromanometric transducers. The tip of a 8F catheter with two piezoelectric transducers and two micromanometers was inserted into a water-filled chamber that had a speaker fixed at one end. The speaker was driven by a power amplifier and sine wave generator. The outputs of the transducers were connected to a low-level amplifier. The piezoelectric transducer behaved as a tunable high-pass filter that could be modified by altering the input impedance of the low level amplifier; the frequency response characteristics were examined at five input impedances ranging from 0.96 to 11.8 megohms. The peak-to-peak outputs of the piezoelectric and pressure transducers were recorded at frequency ranges from DC to 1 kHz with a wide-band oscilloscope. The ratio of the outputs from the piezotransducer and micromanometer (Vph/Vpr) was plotted vs. frequency for each input impedance and analyzed to determine the piezotransducer's output resistance and equivalent capacitance; roll-off frequencies were then calculated. The equivalent capacitance of the piezo-element was determined to be 500-700 picofarads. Series capacitance acted with network resistance to produce a predictable frequency-dependent change in signal amplitude and phase angle. The inherent noise of the pressure transducer was found to be approximately 0.2 mm Hg, while the noise of the piezoelectric transducer was immeasurably low. The piezoelectric phonotransducers were superior to micromanometer transducers in their higher gain and lower noise, suggesting that these transducers may prove useful to physiologic and clinical studies for measuring intravascular sound.

Cardiac Catheterization↗
PubMed1989

Effects of pneumatic antishock garment inflation in normovolemic subjects.

This study examines the effects of inflation of pneumatic antishock garments (PASG) in 10 normovolemic men (mean age 44 +/- 6 yr) undergoing diagnostic catheterization. Seven subjects had normal heart function and no evidence of coronary artery disease (CAD); three patients had CAD. High-fidelity multisensor catheters were employed to simultaneously record right and left heart pressures before PASG inflation and after inflation to 40, 70, and 100 mmHg. A thermal dilution catheter was used to obtain pulmonary capillary wedge pressure and cardiac output. Counterpressure increases greater than or equal to 40 mmHg were associated with significant changes in left and right heart pressures. Right and left ventricular end-diastolic pressures increased 100% (P less than 0.01); mean pulmonary arterial and aortic pressures increased 77 and 25%, respectively (P less than 0.01); systemic vascular resistance increased 22% (P less than 0.05) and pulmonary vascular resistance did not change in normal subjects at maximum PASG inflation. Heart rate, cardiac output, and aortic and pulmonary arterial pulse pressures did not change during inflation in either group. Right and left ventricular end-diastolic pressures and pulmonary capillary wedge pressure were greater (P less than 0.05) in the CAD group compared with the normal subjects during PASG inflation. The data suggest that the primary mechanism whereby PASG inflation induces changes in central hemodynamics in normovolemic subjects is through an acute increase in left ventricular afterload. PASG changes in afterload and pulmonary capillary wedge pressure imply that these devices should be used with caution in patients with compromised cardiac function.

Adult↗
PubMed1989

Heart size and function of soldiers, athletes, and sedentary men.

This study compares the heart sizes and left ventricular masses of soldiers (n = 11) with age- and body size-matched groups of sedentary men (n = 10) and accomplished athletes (n = 11). Echocardiography revealed that active duty soldiers (A) who met minimal fitness standards and pentathletes (P) had greater average left ventricular (LV) end-diastolic volumes (A = 10%, NS; P = 28%, p less than 0.05), stroke volumes (A = 29%, NS; P = 44%, p less than 0.01), and LV masses (A = 22%, NS; P = 76%, p less than 0.01) than sedentary subjects. Athletes had an average LV wall thickness which was 23% (p less than 0.05) greater than that of soldiers and 32% (p less than 0.01) greater than that of sedentary men. The LV wall thickness to radius ratio (h/r) was similar between soldiers and sedentary men, but in athletes the h/r was greater (p less than 0.01) than in the less conditioned subjects. These data suggest that soldiers who meet minimal standards of fitness exhibit cardiac morphometric features consistent with endurance conditioning. However, the soldiers studied were significantly less (p less than 0.001) conditioned than the competitive athletes. These data suggest that improvements in aerobic and cardiac conditioning could be achieved through a greater emphasis on physical training.

Age Factors↗
PubMed1988

Aortic input impedance during Mueller maneuver: an evaluation of "effective length".

Aortic input impedance was calculated in seven subjects in the control state (normal reflection) and during the Mueller maneuver (increased reflection) to evaluate "effective arterial length" under altered physiological conditions. Regional foot-to-foot pulse wave velocities and pressure waveforms along the aorta were used to define an "apparent anatomic length" or distance to a dominant discrete site of reflection "seen" by the ejecting ventricle. Time of wave travel was taken to be one-half the interval from the foot of the incident wave to the midsystolic inflection point. Knowing the time of travel from the returning reflection and velocity, distances calculated to the "apparent anatomic length" were 35 +/- 2 and 34 +/- 2 during control and Mueller maneuver, respectively (P = NS). The frequency of the first minimum of the modulus (fmin) and the first zero crossing of the phase angle (f phi) were determined from the input impedance spectra. During baseline conditions, fmin (3.9 +/- 0.2 Hz) approximately equaled f phi (4.2 +/- 0.2 Hz), and the resulting "effective lengths" calculated using the quarter-wavelength formula were similar to the apparent anatomic length. These data suggested that the aortic region incorporating the renal arterial branches as a site of discrete reflection and that terminal load was not significantly frequency dependent. During Mueller maneuver, however, f min (3.3 +/- 0.2 Hz) and f phi (5.1 +/- 0.2 Hz) were significantly discordant, the terminal load became strongly frequency dependent, and effective length calculated from f min was dissimilar (P less than 0.05) from the unchanged apparent anatomic length.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Ventricular/vascular coupling and regional arterial dynamics in the chronically hypertensive baboon: correlation with cardiovascular structural adaptation.

Ventricular/vascular coupling dynamics and regional hemodynamics of five hypertensive baboons with concentric left ventricular (LV) hypertrophy (mean arterial pressure +/- SD, 148 +/- 16 mm Hg; LV mass/body weight ratio 3.42 +/- 0.8) were compared with five normotensive controls (mean arterial pressure 89 +/- 3 mm Hg; LV mass/body wt ratio 2.73 +/- 0.5) at different mean arterial pressures. Ventricular/vascular dynamics were assessed by aortic input impedance, pulsatile/total power ratio, effective arterial elastance and compliance from a three-element Windkessel "lumped" model of the circulation. Regional arterial dynamics were assessed by pulse-wave velocities and local reflection coefficients. Systemic arterial compliance was similarly decreased with elevated pressure in both groups but was significantly more reduced for the hypertensive group compared with control animals at control (0.49 +/- 0.16 vs. 0.96 +/- 0.09 ml/mm Hg; p less than 0.05) and acutely lowered arterial pressure (0.62 +/- 0.26 vs. 1.41 +/- 0.24 ml/mm Hg, respectively). Changes in compliance were paralleled by differences in effective arterial elastance derived from cineventriculographic pressure-volume ratios. Regional foot-foot and apparent phase pulse-wave velocities were significantly increased for distal aortic segments of the hypertensive animals during elevated pressures compared with controls (cff, 17.5 +/- 7.5 vs. 8.7 +/- 3.0 m/sec; p less than 0.05). Histology of the aorta revealed significant increases in collagen content (microgram/mg dry wt) from proximal to distal aortic segments (27 +/- 2 vs. 38 +/- 6; p less than 0.005) in hypertensive animals but not in controls (27 +/- 2 vs. 32 +/- 6; NS). With pharmacological normalization of systemic arterial pressures, hypertensive baboons developed aortic wave speeds similar to controls but manifested significantly reduced compliance compared with controls. In contrast, with acute elevations of pressure, systemic arterial aortic compliances were similar for both groups, but distal pulse-wave velocities were significantly increased for hypertensive animals compared with controls. We conclude that measures of ventricular/vascular coupling and arterial dynamics are determined by both the level of arterial pressure and the physical characteristics of the cardiovascular system in chronic systemic hypertension and pressure overload ventricular hypertrophy.

Adaptation, Physiological↗
PubMed1987

Nonhuman primate model for regional wave travel and reflections along aortas.

Arterial pulse transmission and wave reflections were studied in five mature anesthetized baboons (Papio anubis) using multisensor micromanometry. Simultaneous pressures were recorded from the left ventricle and every 10 cm along the aorta and its terminal branches, and flow velocity was measured in the aortic root. Aortic input impedance and regional foot-to-foot and apparent phase velocities were calculated. Aortography provided dimensional data for local reflection coefficients. Regional foot-to-foot wave speeds were somewhat lower than corresponding segments in humans. Proximal aortic pressure waveforms and characteristic impedance (110 +/- 29 dyn X s X cm-5) were not characteristic of middle-aged humans. Reflection coefficients at the terminal aortic bifurcation (0.06) at the level of the renal artery branches (0.09) were less than those found in humans. We conclude that the junction of the renal artery branches and the aorta in the baboon is closely matched and represents much less of a discrete reflection site than in humans. Although the baboon may be used to study pulse transmission characteristics in the baboon, this species is not a good model for the proximal systemic reflective characteristics of normal middle-aged humans.

Animals↗
PubMed1987

Effects of physical conditioning on the heart size and wall thickness of college women.

M-mode echocardiograms were obtained from 40 sedentary college women, 8 sprinters, 6 distance runners, 10 swimmers, 9 basketball players, 8 dancers, and 10 sedentary men (ages 19 to 31 yr). Treadmill stress tests were performed by all groups except the basketball players. The aerobic capacities of the athletes were 30 to 48% greater (P less than 0.05) than the sedentary subjects. The athletes exhibited trends toward higher than average left ventricular (LV) end-diastolic dimensions (7 to 25%), LV end-diastolic volumes (12 to 53%), stroke volume (13 to 52%), LV mass (11 to 42%), and left atrial dimensions (6 to 31%) when data were standardized for body surface area. A correlation (r = 0.323, P less than 0.05) was noted between LV mass index and maximal oxygen uptake when data were pooled. Ten sedentary women and ten age-matched sedentary men were endurance-conditioned by 10 wk of running. Both sexes increased maximal oxygen uptake approximately 20% (P less than 0.05) and exhibited similar changes in LV wall thickness, end-diastolic dimension, end-diastolic volume, and mass. These changes regressed within 10 wk after the termination of conditioning. This study suggests that women athletes exhibit cardiac morphologic features which resemble that reported for their male counterparts and that the cardiac response of sedentary men and women to modest levels of endurance conditioning is similar.

Adult↗
PubMed1986

Hemodynamic response to rapid pneumatic antishock garment deflation.

Irreversible hypotension with subsequent cardiovascular collapse has been reported as a catastrophic complication of inappropriate pneumatic antishock garment (PASG) deflation. This study was undertaken to analyze the cardiodynamic response by which PASG deflation produces hypotension. Five normovolemic patients undergoing cardiac catheterization for atypical chest pain syndrome volunteered for this study. Serial measurements of right atrial, right ventricular, pulmonary artery, left ventricular, and aortic pressures were obtained with subjects supine at the following times: prior to inflation of the PASG; during PASG inflation at 100 mm Hg; and during rapid PASG deflation. Pulmonary and aortic flow velocities were recorded in two patients. The application of external pressure with PASG produced a significant increase in left and right heart pressures (P less than .05). Sudden PASG deflation produced significant transient hypotensive changes (P less than .01). When PASG deflation hemodynamics were compared to preinflation data, mean arterial pressure decreased 14 mm Hg (P less than .01); mean pulmonary pressure decreased 6 mm Hg (P less than .01); and mean right atrial and left ventricular end-diastolic pressures decreased 4 and 6 mm Hg, respectively (P less than .01). An analysis of right and left heart hemodynamic data suggests that the early hypotensive response associated with PASG deflation is consistent with a reduction in left ventricular afterload followed by a decrease in preload.

Adult↗
PubMed1986

Left ventricular performance of the athletic heart during upright exercise: a heart rate-controlled study.

This study compares the left ventricular performance of chronically conditioned pentathletes (N = 10) with less-conditioned subjects (N = 10) during dynamic upright exercise. The pentathletes were found to have a superior treadmill performance [24 +/- 4 vs 17 +/- 2 min (SD), P less than 0.01], reduced resting heart rate (41 +/- 13 vs 62 +/- 6 bpm, P less than 0.01), and increased left ventricular mass (254 +/- 85 vs 179 +/- 35 g, P less than 0.05) compared to the control group. Radionuclide ventriculography and heart rate controlled-bicycle ergometry were employed to examine changes in left ventricular ejection fraction, end-diastolic volume, end-systolic volume, and stroke volume. Heart rate was controlled by adjusting the resistance of the ergometer until stable heart rates of 90, 110, 130, and 150 bpm were achieved. Following heart rate stabilization, 99mTc images were acquired during 3-min stages at each target heart rate level. In the pentathletes, left ventricular ejection fraction, end-diastolic volume, and stroke volume increased (P less than 0.01) during exercise, and end-systolic volume tended to decrease. No difference was noted in left ventricular ejection fraction between groups when heart rates were matched. However, the exercise-induced changes in end-diastolic volume and stroke volume were greater (P less than 0.01) in the pentathletes. In conclusion, the athletes studied relied on the same mechanism as the less-conditioned subjects for improving pump performance during exercise stress, but the athletes' ability to mobilize a greater end-diastolic volume accounts for their larger stroke output during each stage of heart rate-matched exercise.

Adult↗
PubMed1986

Supplemental chloralose anesthesia in morphine premedicated dogs.

This study evaluated the cardiorespiratory stability of six dose-regulated, 12-hour, chloralose anesthetic maintenance protocols. Thirty mongrel dogs were premedicated with morphine sulfate (5mg/kg) and anesthetized with an induction dose of chloralose (80mg/kg). Fifteen animals were permitted to breathe spontaneously and 15 animals were ventilated mechanically to maintain a constant arterial pCO2 (40 +/- 5 mmHg). The spontaneously breathing dogs were separated into three groups in which animals (n = 5) were given different bolus doses of supplemental anesthetic. Initially the spontaneously breathing animals were hypoxemic, acidemic and hypercapnic. No consistent hemodynamic difference was noted among these groups. The mechanically ventilated animals were also divided into three groups that received varying doses of supplemental chloralose by constant infusion. Significant (p less than 0.01) myocardial depression was noted in the heavy-dosed animals by the third hour. Systolic pressure decreased 44%, pulse pressure decreased 37% and peak left ventricular dP/dt decreased 52%. All heavy-dosed animals expired before the eighth hour. Although these data suggest that morphine-premedicated, chloralose-anesthetized animals generally provide a stable cardiopulmonary model, high-dose chloralose supplementation depressed ventilation and produced a dose-dependent cardiotoxicity.

Anesthesia↗
PubMed1985

Regional wave travel and reflections along the human aorta: a study with six simultaneous micromanometric pressures.

The human aorta and its terminal branches were investigated in normal subjects during elective cardiac catheterization to evaluate regional wave travel and arterial wave reflections. A specially designed catheter with six micromanometers equally spaced at 10 cm intervals was positioned with the tip sensor in the distal external iliac artery and the proximal sensor in the aortic arch. Simultaneous pressures were obtained and analyzed for foot-to-foot wave velocity, and Fourier analysis was used to derive apparent phase velocity. These quantities were assessed during control (n = 9), during Valsalva (n = 8) and Müller (n = 4) maneuvers, and during femoral artery occlusion by bilateral manual compression (n = 8). During control, regional cross-sectional areas, determined from aortography, and regional foot-to-foot pulse wave velocities were used to calculate the local reflection coefficient in the proximal descending aorta (gamma = 0.05), at the junction of the renal arteries (gamma = 0.43), and at the terminal aortic bifurcation (gamma = 0.13). To test the hypothesis that significant reflections originate in the aorta, at the level of the renal arteries, aortograms were used to design a latex tube model with geometric properties similar to the descending aorta. Velocities and reflection characteristics in the model and in vivo were compared. Inspection of thoracic aortic pressures under control conditions revealed a reflected wave originating from the region of the aorta at the level of the renal arterial branches while abdominal pressures exhibited reflection from a site peripheral to the terminal aortic bifurcation. In the low frequency range, apparent phase velocity was found to be higher proximal to the renal arteries as compared with at the distal sites. In addition, the minimum value occurred at a higher frequency in the lower thoracic aorta than at more distal sites. The effects of reflection on apparent wave velocity in the tube model were consistent with data obtained in vivo. The Valsalva maneuver diminished the reflection from the aortic region of the renal arteries, thus allowing the distal reflected wave to become more evident on the thoracic pressure waveforms. Bilateral femoral artery occlusion usually enhanced the distal reflection and the Müller maneuver usually resulted in small increases in reflections. In conclusion, the geometric and elastic nonuniformity of the aorta results in two major sites of arterial wave reflection that influence the aortic pressure waveforms in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

Left ventricular volume determination from single-photon emission computed tomography.

To compare the accuracy of single-photon emission computed tomography (SPECT) with that of contrast cineangiography in measuring left ventricular end-diastolic volume, 25 consecutive patients undergoing catheterization for coronary artery or valvular heart disease were first evaluated scintigraphically. A simple, count-corrected voxel counting technique was used to derive left ventricular end-diastolic volume from transaxial SPECT slices. SPECT volume values showed a high degree of correlation with those determined by angiography (r = 0.969), with a standard error of the estimate of 23 ml. SPECT offers a highly accurate and essentially noninvasive method for measuring chamber volumes that is independent of geometric assumptions about ventricular configuration and chest wall attenuation and does not require blood sample counting.

Adult↗