Stroke Volume Values Research Articles

Comparative Assessment of Hemodynamics in Cardiosurgical Patients

The results of comparative determination of the values of stroke volume (SV) and cardiac index measured by integral rheography (IRG) after M. I. Tishchenko, thermodilution (using a Swan-Ganz catheter), and echocardiography (EchoCG) were studied in 139 patients with acquired heart diseases (AHD) and coronary heart disease (CHD) in different periods after cardiosurgical operations under extracorporeal circulation. The reasons for lowering SV measured by rheography were revealed. The changes in the oscillations of terminal circulatory vessels, which are associated with altered ejection fraction and decreased capillary blood flow velocity pulse under the action of different doses of adrenaline, were shown to affect the genesis of rheograms. The problem in assessing the nature of blood flow (pulsation) in the terminal portion of the circulatory system in emergency medicine is discussed.

Biventricular pacing with left to right ventricle pacing delay - the acute hemodynamic effect

Newer pacemakers designed for CRT have the possibility to program a delay between paced ventricles (VV delay). There is some evidence that VV delay optimization in biventricular pacing (BiVp) may bring an additional hemodynamic benefit of CRT. Most of the CRT studies conducted so far were performed with no VV delay programming possibility. of the study was to compare acute hemodynamic effects of BiV pacing using different times of right ventricle (RV) after left ventricle (LV) delay. The study group consisted of 71 patients (59M, 12F; mean age 67,2 y.) with permanently implanted BiVp system with the possibility to set the VV delay. RV lead: 49 pts - RVA, 22 pts RVOT. Measurements were performed by means of impedance cardiography (BioZ.com). Stroke Volume (SV), Velocity index (VI), Acceleration Index (ACI) as well Ejection Time (LVET) and Preejection period (PEP) were determined. The measurements in 3 min periods were collected and averaged, after the adaptation periods of 3 min throughout different VV delay pacing modes (0/4ms, 15/16ms, 30/32ms, 50/52ms and 72/75ms, depending on the pacemaker). Mean SV values increased as VV delay was prolonged, from the lowest at 0ms VV delay to the highest at 75ms VV delay (62,4; 62,7; 62,9; 64,9; 65,6 ml respectively; ANOVA p<0,001). Different responses were observed in individual patients, however 75ms delay was the best setting in 36,6% and 0ms the worst in 31,0% of pts. The mean intrapatient difference between BiVp with no delay and the best one was 6,9ml (>10%) (p<0,001). Sequential BiVp compared to BiVp with no VV delay brings the additional hemodynamic improvement in acute setting. In the majority of patients the VV delay of 75 ms is the most beneficial and no delay is the least beneficial. Because of inter-patient differences, the VV delay should be optimized in every case of BiVp.

Comparison of a small volume of hypertonic saline solution and dextran 40 on hemodynamic alternations in conscious calves

The hemodynamic effects of rapid intravenous (IV) administration of 10% dextran 40 in saline solution (D40) and 7.2% hypertonic saline solution (HSS) in calves were compared. Calves received isotonic saline solution (ISS), HSS or D40 (3 calves/group) and were monitored of blood pressure, and cardiac output (CO) for 180 min. HSS and D40 infusions induced a significant increase in relative plasma volume reaching 134.9+/-2.8 and 125.0+/-1.9%, respectively at the end of fluid infusion. In the HSS group, CO, cardiac index (CI) and stroke volume (SV) remained constant at low levels after 90 minutes despite the maximal values of CO, CI and SV at the end of infusion, reaching 21.0+/-6.3 l/min (p<0.05), 177.8+/-14.2 ml/min/kg (p<0.001) and 0.20+/-0.03 l/beat (at t=10 min, p<0.001), respectively. In contrast, CI and SV in the D40 group showed significant increases to 14.7+/-2.9 l/min and 153.5+/-17.2 ml/min/kg, respectively, at the end of fluid infusion. And those values remained constant at higher levels than those of the before infusions values throughout the experimental periods. Positive effects for hemodynamic alternations of D40 in calf practice were milder and longer than those of HSS. Therefore, the D40 infusion should be explored as a possible treatment for dehydrated calves, since rapid infusion of D40 may be safe and more beneficial for rehydrating more than HSS treatment.

Comparability of Spot Versus Band Electrodes for Impedance Cardiography.

Although band and spot electrodes have been compared in prior research, they have not been evaluated (a) at identical anatomical locations, (b) during a single laboratory session, (c) with measures taken in close temporal proximity, (d) using a single impedance cardiograph unit, or (e) using sufficiently powerful statistical tests. Thirty-one healthy young adults completed a psychophysiological assessment which consisted of baseline, mental arithmetic stressor, and recovery conditions. Data from spot and band electrodes were collected by alternating between electrode types every minute of the experiment. Correlations between spot and band electrodes at absolute levels of all cardiovascular measures (cardiac output, impedance derivative, basal impedance level, Heather index, heart rate, left ventricular ejection time, pre-ejection period, stroke volume) were of high magnitude (ravg = .78), while the correlations for difference scores were lower (ravg = .50). Analyses of mean levels indicated spot electrodes yielded significantly lower values for the impedance derivative, Heather index, and basal impedance, and higher values for cardiac output and stroke volume, than band electrodes. The advantages and disadvantages associated with spot and band electrode configurations, as well as their use in ambulatory recording, are discussed.

Heart rate deflection point as a strategy to defend stroke volume during incremental exercise

The purpose of this study was to examine whether the heart rate (HR) deflection point (HRDP) in the HR-power relationship is concomitant with the maximal stroke volume (SV(max)) value achievement in endurance-trained subjects. Twenty-two international male cyclists (30.3 +/- 7.3 yr, 179.7 +/- 7.2 cm, 71.3 +/- 5.5 kg) undertook a graded cycling exercise (50 W every 3 min) in the upright position. Thoracic impedance was used to measure continuously the HR and stroke volume (SV) values. The HRDP was estimated by the third-order curvilinear regression method. As a result, 72.7% of the subjects (HRDP group, n = 16) presented a break point in their HR-work rate curve at 89.9 +/- 2.8% of their maximal HR value. The SV value increased until 78.0 +/- 9.3% of the power associated with maximal O(2) uptake (Vo(2 max)) in the HRDP group, whereas it increased until 94.4 +/- 8.6% of the power associated with Vo(2 max) in six other subjects (no-HRDP group, P = 0.004). Neither SV(max) (ml/beat or ml.beat(-1).m(-2)) nor Vo(2 max) (ml/min or ml.kg(-1).min(-1)) were different between both groups. However, SV significantly decreased before exhaustion in the HRDP group (153 +/- 44 vs. 144 +/- 40 ml/beat, P = 0.005). In the HRDP group, 62% of the variance in the power associated with the SV(max) could also be predicted by the power output at which HRDP appeared. In conclusion, in well-trained subjects, the power associated with the SV(max)-HRDP relationship supposed that the HR deflection coincided with the optimal cardiac work for which SV(max) was attained.

Stroke volume and systolic time intervals: Beat-to-beat comparison between echocardiography and ambulatory impedance cardiography in supine and tilted positions

The aim of the study was to compare stroke volume (SV), ejection time (ET) and pre-ejection period (PEP) measurements obtained using a central haemodynamics ambulatory monitoring device based on impedance cardiography (ICG), in supine and tilted positions (60 degrees), with pulsed Doppler echocardiography as a non-invasive reference method. The Holter-type ICG device was used for off-line, beat-to-beat, automatic determination of SV, ET and PEP. ICG data were compared with those obtained simultaneously using pulsed Doppler echocardiography in the ascending aorta from a suprasternal projection, 1 min before and 10 min after tilting. The tests were performed in 13 young, healthy subjects (six men and seven women, aged 23-33 years). Linear regression between the measured values obtained for all subjects was described by the following formulas: SVicg= 13.9 + 0.813 x SVecho (r = 0.857, SEE = 9.03, n = 496), ETicg = 16.8 + 0.987 x ETecho (r = 0.841, SEE=21.3, n = 496), PEPicg= 22.8 + 0.890 x PEPecho (r = 0.727, SEE = 14.6, n = 496). The data showed that ambulatory impedance cardiography gives useful absolute values of SV and systolic time intervals measured in supine and tilted positions.

Blood Pressure Response to Uncomplicated Hemodialysis: The Importance of Changes in Stroke Volume

Background: The cause of blood pressure (BP) changes during uncomplicated hemodialysis (HD) has not been fully investigated. Controversy exists whether changes in BP result from changes in stroke volume (SV) or total peripheral resistance (TPR). Methods: We investigated 19 patients using continuous BP monitoring (Portapres^®) and subsequent Modelflow^® analysis, yielding continuous SV, cardiac output (CO) and TPR values. Blood volume (BV) monitoring was also performed. For each patient, the sensitivity index (SI) was calculated. The SI is the slope of the curve depicting the relationship between the systolic BP (SBP) response and the BV response. The patients were divided into two groups: group A had an SI >1 which means a decrease in SBP in response to BV change, and group B had an SI <1. In these patients, SBP remained stable despite a BV change. Results: Baseline characteristics and baseline values of all parameters were similar between the groups. In group A, SBP decreased by 25 ± 19 mm Hg and in group B the SBP increased by 5.0 ± 29 mm Hg (p < 0.05), while BV change was similar (10.6 ± 4.9 and 11.2 ± 4.2%, respectively). The difference in SBP response was caused by a different SV response (group A –44 ± 16% and group B –26 ± 18%, p = 0.04), while the TPR response was similar (71 ± 27% in group A vs. 59 ± 58% in group B). Conclusion: Patients responding with a BP decrease to BV reduction during uncomplicated HD differ in their SV response from patients with a stable BP.

Circulatory responses to progressive exercise: insights from positional differences.

The influence of body position on cardiac responses to progressive exercise was examined in 13 healthy circumpubertal boys. The subjects (mean age 12.5 +/- 1.4 y) performed a progressive cycle test with an identical protocol in the sitting and supine positions. Stroke volume and left ventricular dimensions were assessed with Doppler and two-dimensional echocardiography, respectively. During supine exercise, no changes were seen in stroke volume or left ventricular preload (end-diastolic dimension) with increasing exercise intensity. At rest, mean values for stroke volume and cardiac output were 16.4 % and 27.1 % lower, respectively, with subjects upright compared to supine. With upright exercise these variables rose to become insignificantly different than supine values. Stroke volume while cycling upright rose by 29 % by the second workload but remained stable at higher work intensities. The initial increase in stroke volume observed only when cycling upright presumably reflects mobilization of dependent blood in the lower extremities. The mechanisms governing cardiac responses to exercise when supine and upright are otherwise identical.

705 Rright ventricular apex or outflow tract for biventricular pacing

It was proved that RVOT pacing makes less ventricular asynchrony than RVA pacing. Recently better LV leads permits pacing more distal part of cardiac veins. For avoidance of apical region pacing of both of ventricles we implanted RV lead in RVOT position in every second patient with BiV pacing system. The aim of the study was to compare acute hemodynamic effects of BiV pacing in patients with RV lead in RVA and RVOT position. The study group consisted of 18 patients with permanently implanted biventricular pacing system (atrio-ventricular pacing 12 pts, ventricular only pacing 6 pts). RV lead positions: RVA 10 pts., RVOT 8 pts. LV lead positions: lateral CV 7 pts., postero-lateral CV 10 pts., posterior CV 1 pt. Hemodynamic measurements were performed using impedance cardiography (BioZ.com ICG; Cardiodynamics). Indices of contractility: Acceleration Index (ACI), Velocity Index (VI) and Stroke Volume (SV) were determined. Six consecutive measurements were collected after the adaptation period of 2 minutes throughout RV and BiV pacing in turn. The data for each pacing mode were averaged and compared. Results: ACI, VI and SV values were significantly higher during BiV pacing in comparison to RV pacing.

Examination of the heart capacity of meat- and fat-type pigs by means of ECG-gated dynamic magnetic resonance imaging and computerized tomography

The cardiovascular capacity of animals is considerably affected by the selection procedure for high lean meat production. To determine the genotype and live weight-related changes of some quantitative characteristics of the pig heart function, serial measurements were carried out. Intensive meat (Hungarian Large White×Belgian Landrace×Pietrain×Norvegian Landrace) and extensive fat type (Mangalica) pigs were examined using whole body magnetic resonance imaging (MRI) and a spiral computer tomograph (CT). Based on our dynamic MRI examination, the following live weight-dependent significant differences were found. (1) The means of the measured left ventricular stroke volume values were at body weights of 30, 60 and 90 kg: 29.1, 41.2, 63.5 and 38.1, 54.0, 55.8 ml in case of meat- and fat-type pigs, respectively. (2) The average cardiac output (CO) values were: 3.8, 4.4, 5.8 and 3.1, 3.9, 3.8 l/min. (3) The estimated relative CO value (skeletal muscle tissue volume measured by CT/CO unit) of the meat- and fat-type pigs were 4.0, 5.6, 6.0 and 2.4, 3.9, 4.8 dm 3/(l min −1), respectively, in sedentary conditions. The significant genotype effect measured with this in vivo method in the relative CO values demonstrates the usability of this technique in selection.

Haemodynamic monitoring during high-frequency oscillatory ventilation in adults

High-frequency oscillatory ventilation (HFOV) has been described as an effective therapy of RDS in prematurities and neonates. However, there are only few reports about using this technique in adults. The main goals of our study were establishing, during adult ventilation, the optimal parameters for monitoring HFOV, relative risk of hemodynamic disturbances connected with HFOV, and contraindications for HFOV. Until the present time six patients were enrolled to the study. The indications were: unsuccessful classical ventilation (CMV + PEEP + Plateau for at least 6 hours), or unsuccessful weaning (routine procedure for at least 7 days). After qualification all patients were ventilated using the SensorMedics 3100B oscillator. The following parameters were continuously measured: cardiac output using the Doppler technique (Abbott monitor), heart rate, blood pressures (systolic, diastolic, mean), EKG, SaO2, and ETCO2. Every hour CVP, arterial gases and diuresis were measured. In all patients a rapid increase in PaO2 was observed, which enabled progressive decrease in FiO2(20–40%). After several hours of HFOV the condition of two patients deteriorated and it was necessary to immediately resume classical ventilation. One of these patients was morbidly obese (BMI = 43.2), whereas the other had critically low ejection fraction (14.3%) and low cardiac output (2.7–3.4 l/min). The first symptom of disturbances was a decrease of signal and amplitude of the plethysmographic curve. At that moment PaCO2 was 34.2 and 47.0 mmHg, respectively, and cardiac output was a little higher than initially. Another symptom was the disappearance of pleth signal. The next symptom was bradycardia and a sudden decrease of cardiac output (30–50%), while the stroke volume value remained unchanged. After resuming classical ventilation (CMV mode) and hemodynamic stabilization, a temporary increase of PaCO2 was observed (60.1 and 65.3 mmHg). We concluded that: 1) The documented scenario of the deterioration was different from that typically observed during classical ventilation; 2) The SaO2 and pleth curve monitoring during HFOV is essential for safety reasons; 3) The first symptom of deterioration during HFOV may be the decrease of amplitude and signal of the pleth curve; 4) The disappearance of the pleth signal is a sign of an imminent deterioration during HFOV; 5) The arterial gas analysis may not give sufficient information about the patient's condition; 6) Significant obesity and left ventricular insufficiency may be contraindications for HFOV in adults.

Hypokinetic circulation in persons with paraplegia.

It is well established that hemodynamic dysfunction, resulting in diminished upper-extremity work capacity, occurs in persons with spinal cord injury (SCI) as compared with those who are nondisabled (ND). Although it has been shown that persons with paraplegia display higher values of heart rate (HR) with lower values of stroke volume (SV) during exercise, it is not resolved whether there is adequate compensation to produce similar values of cardiac output (.Q) as in ND. This study examined central cardiovascular responses (HR, SV, and .Q) of 20 subjects with complete thoracic level SCI (T(4)-T(11)) and 20 sedentary ND subjects during matched levels of arm-crank (AC) exercise. All subjects performed an incremental peak AC test to volitional exhaustion with continuous metabolic analysis and HR measurement via open circuit spirometry and 12-lead electrocardiography, respectively. Stroke volume was assessed using transthoracic impedance. Heart rate was higher for SCI (P< 0.05) with significantly lower values for SV and .Q at rest (approximately 25%). Peak responses were significantly higher for ND in all factors except HR. Although subpeak HRs at matched absolute workloads were significantly higher for SCI (12-20 beats.min (-1) ), SV and .Q were significantly lower (P< 0.05). The results of this study indicate that .Q is significantly lower in SCI than in ND during AC, despite significantly greater values of HR. These findings also suggest that the disparity in exercise values of .Q is related to differences exhibited at rest.

Cardiovascular Responses to Progressive Cycle Exercise in Healthy Children and Adults

The aim of this study was to compare resting, relative submaximal (at the same percentage of maximal oxygen uptake) and maximal cardiovascular responses to progressive cycle exercise in pre-pubertal children and young adults with similar aerobic aptitude. Fourteen healthy children (7 girls and 7 boys) with a mean age of 10.8 yr and 16 healthy young adults (8 women and 8 men) with a mean age of 22.4 yr underwent a progressive cycle test until exhaustion with estimation of stroke volume and cardiac output by Doppler echocardiography. Submaximal responses were evaluated at similar exercise intensities (around 40, 60 and 80 % of maximal oxygen uptake). Mean submaximal and maximal oxygen uptake were not significantly different between the children and the adults. As expected, the adults demonstrated larger absolute values of stroke volume and cardiac output at all levels of intensity but when related to body surface area, the differences disappeared. The relationships between cardiac output and oxygen uptake calculated from comparable submaximal intensities were similar (slopes and intercepts) in the children and the adults. According to these results, it seems that the lower cardiovascular responses to exercise in children may be attributed to their smaller heart size.

In vitro cardiac performance in triploid brown trout at two acclimation temperatures

The maximum values for heart rate (fH), stroke volume (VH), cardiac output (Q) and myocardial power output, measured in vitro with a perfused heart preparation, as well as the isometric force‐frequency relationship for atrial and ventricular muscle strips, in triploid brown trout Salmo trutta were all comparable with established information for diploid rainbow trout Oncorhynchus mykiss. Therefore, it was concluded that triploidy is not associated with a major deficiency in maximum cardiac performance. However, a heightened sensitivity to ryanodine was discovered, which indicated an enhanced role for the sarcoplasmic reticulum in excitation‐contraction coupling in these triploid fish. It is suspected that the enhanced role of the ryanodine receptor may be a cellular compensation related to larger cardiac myocytes. It was also clearly established that there was a plateau in maximum cardiac performance between 14 and 18° C and this plateau might be a contributing factor to the reduced factorial aerobic scope and increased fish mortality observed at 18° C.

Relation of hemodynamics and risk factors to ventricular-vascular interactions in the elderly: the Cardiovascular Health Study.

To investigate the interaction between left ventricular (LV) geometry, carotid structure and arterial compliance in relation to hemodynamic stimuli and risk factors (plasma cholesterol, body mass index, insulin resistance, smoking habit, age, sex and race). Cross-sectional. Echocardiography and carotid ultrasound were performed in 2375 elderly subjects without signs or history of prevalent cardiovascular disease, diabetes or renal disease (795 men; 298 non-whites; 1215 hypertensive), from the cohort of the Cardiovascular Health Study. Arterial compliance was estimated by the prognostically validated ratio of stroke volume to pulse pressure (SV/PP) as the percent deviation (Delta%) from the value predicted by individual age, heart rate and body weight. Intima-medial thickness (IMT) was higher in the presence of LV hypertrophy (LVH) in normotensive and hypertensive subjects and was greatest in the presence of concentric LVH. Maximum carotid lumen diameter (CLD) was also higher in the presence of LVH (and was greatest with eccentric LVH, in association with relatively high values for stroke volume). After adjusting for blood pressure, maximum carotid lumen diameter was directly correlated with stroke volume, and IMT to LV mass (all P < 0.001). Similarly, IMT was also related to maximum carotid lumen diameter, independently of prevalent risk factors (P < 0.001). SV/PP-Delta% was reduced in both groups with concentric LV remodeling (both P < 0.0001) or concentric LVH (both P < 0.05). Adjusting for risk factors did not affect these associations in normotensives, but made them insignificant in hypertensives. In normotensives, IMT was inversely related to SV/PP-Delta% (P < 0.001), independently of risk factors, whereas no significant relation was found in hypertensives. The magnitudes of carotid intima-medial thickness and lumen diameter parallel levels of LV mass and geometry, and are directly related to stroke volume and arterial stiffness; this interaction is most evident in the presence of normal blood pressure, whereas it is affected by other cardiovascular risk factors when arterial hypertension is present.

A report on physical performance in female patients diseased for idiopathic scoliosis

The purpose of this study was to examine physical performance and exercise tolerance in patients with scoliosis in comparison with healthy girls of the similar age. Results of the study show the similar aerobic performance in both groups. However, exercise tolerance was significantly lower in patients with scoliosis than in the control group. Similarly, resting values of cardiac output and stroke volume were significantly lower in girls with scoliosis as compared with healthy girls.

M‐MODE AND DOPPLER ECHOCARDIOGRAPHIC FINDINGS IN NORMAL FERRETS SEDATED WITH KETAMINE HYDROCHLORIDE AND MIDAZOLAM

M-mode and Doppler echocardiographic values were obtained from 30 normal adult ferrets (14 neutered females, 13 neutered males, 3 intact males) sedated with an intramuscular combination of ketamine hydrochloride and midazolam. Routine M-mode measurements of the left and right ventricle, left atrium (LA) and aorta (AO) and Doppler measurements of aortic and pulmonic outflow, and mitral inflow were recorded. The following values were calculated: LA:AO diameter, ratio of peak E: peak A wave velocity (E:A ratio) for mitral inflow, and stroke volume (SV), cardiac output (CO) and cardiac index (CI) for both pulmonary and aortic outflow tracts. Maximal aortic velocities (AOmax) and velocity-time integral values (AO VTI) were significantly less than corresponding pulmonary outflow tract values (PAmax, PA VTI) but there was no difference in calculated values for SV, CO or CI. Calculated CO values were in the range expected based on the size of the species. Difficulties in aligning the aortic outflow tract for Doppler imaging may make pulmonary outflow Doppler values more consistent for use in estimating volume flow in ferrets.

Physiological Assessment of Bagpipers: A Preliminary Study of Cardiopulmonary Parameters

This study examined pulmonary function of pipers and cardiac adaptation to the playing of the Great Highland bagpipe. Pipers (n = 13) of varying ages (31-65 years) and playing experiences (2-20+ years) were evaluated for vital capacity (VC), maximal voluntary ventilation (MVV), and forced vital capacity (FVC) using a RIKO AS-600 spirometer. Subjects were monitored by impedance cardiograph for heart rate (HR), stroke volume (SV), and cardiac output (CO) at rest and during 5 minutes of playing. An automatic blood pressure (BP) monitor collected BP values over the same time period. Eleven weeks after initial cardiac data collection, the BP and cardiac measurements were repeated using the same protocols. Mean values for HR, SV, and CO were calculated for rest and each minute (1-5) of playing. A 2 (data session) by 6 (rest, min 1–5) repeated-measures ANOVA was performed. Analysis revealed a significant overall time effect (p &lt; 0.001) on HR. A-priori contrast comparing all playing times with rest showed significant differences at all time points. Analysis of SV and CO failed to find significance. Heart rate values calculated for percent of maximum ranged from 68% to 89% of maximum overall while playing (session 1) and from 55% to 81% of maximum (session 2). Predicted percent of maximum values for VC and MVV found 77% of players above their maximum predicted values.

EFFECTS OF FIVE CONSECUTIVE DAYS OF INTERMITTENT PNEUMATIC COMPRESSION ON CARDIAC FUNCTION.

57 Increasing venous return is thought to be responsible for enhancing various cardiac parameters, including heart rate (HR), cardiac output (CO), stroke volume (SV), left ventricular end systolic volume (LVESV), and ejection fraction (EF). Use of intermittent pneumatic compression is thought to increase venous return. A compression stimulus might be similar to an exercise training stimulus, which has been shown to change cardiac function in as little as five days. The purpose of this study was to determine whether five consecutive days of compression therapy would cause baseline changes in the above parameters, using a new compression device. Ten healthy male subjects aged 44 +/− 5 y and weighing 92 +/− 19 kg participated in this study. Each subject underwent five consecutive days of compression, in which limbs were compressed intermittently at 2 psi for 45 minutes each day. Cardiac parameters were measured on days 1 and 5 using thoracic impedance. Results demonstrated an ejection fraction of 0.54 and 0.53 on days 1 and 5, respectively. For LVEDV, values were 203.8 ml and 200.4 ml, and for LVESV values were 97.5 ml and 97.4 ml. Day 1 and Day 5 baseline values for SV were 106 ml and 103 ml; 7.4 l/m and 7.1 l/m for CO, and 71 bpm and 70 bpm for HR. None of these differences were significant. In conclusion, these results suggest that five days of intermittent compression treatment does not affect baseline cardiac parameters.

Effects of wave reflection timing on left ventricular mechanics

The aim of this study was to evaluate how the timing of the pressure pulse produced by peripheral reflection affects the left ventricle (stroke volume, ventricular work, coronary driving pressure). Ten isolated perfused rabbit hearts were attached to rubber tubes of different lengths (0.5, 0.8 and 1 m) connected to a hydraulic resistance. The different lengths produced reflections at different times and the reflected pulse returned to the ventricle in early (at 84 ms), middle (at 134 ms) and late systole (at 168 ms) for the three tubes, respectively. The loading parameters (ventricular filling pressure and hydraulic resistance) were not changed during the procedure. Ventricular and aortic pressure and aortic flow were monitored continuously and recorded; cardiac cycle was fixed at 800 ms. An operator-independent procedure was used to calculate instantaneous and total systolic external work, mean diastolic aorto-ventricular pressure difference and ventricular stroke volume. Results: The mean value of stroke volume for the three different length rubber tubes was 320±71, 348±77 and 368±87 μl, respectively. The mean value of total external work was 20.3±8.3, 22.5±8.8 and 24.2±9.6 mJ, respectively. The mean aorto-ventricular pressure difference was 40±12, 46±13, 50±14 mmHg, respectively (1 mmHg=133 Pa). The differences between the parameters measured in the three conditions were statistically significant ( p<0.05). A reduction of reflection timing, reduces, on a pure mechanical basis, cardiac output and external ventricular work and has a negative effect on coronary driving pressure.