Targeted disruption of the gene for natriuretic peptide receptor-A worsens hypoxia-induced cardiac hypertrophy

Targeted disruption of the gene for natriuretic peptide receptor-A (NPR-A) worsens pulmonary hypertension and right ventricular hypertrophy during hypoxia, but its effect on left ventricular mass and systemic pressures is not known. We examined the effect of 3 wk of hypobaric hypoxia (0.5 atm) on right and left ventricular pressure and mass in mice with 2 (wild type), 1, or 0 copies of Npr1, the gene that encodes for NPR-A in mice. Under normoxic conditions, right ventricular peak pressure (RVPP) was greater in 0 than in 2 copy mice, but there were no genotype-related differences in carotid artery PP (CAPP). The left ventricular free wall weight-to-body weight (LV/body wt) ratio was greater in 0 than in 2 copy mice and there was a trend toward a greater right ventricular weight-to-body weight (RV/body wt) ratio. Three weeks of hypoxia increased RVPP and RV/body wt in all genotypes. The increase in RVPP was similar in all genotypes (11-14 mmHg), but the hypoxia-induced increase in RV/body wt was more than twice as great in 0 copy mice than in 2 copy mice (1.11 +/- 0.06 to 2.65 +/- 0.46 vs. 0.96 +/- 0.04 to 1.4 +/- 0.09, P < 0.05). Chronic hypoxia had no effect on CAPP in any genotype and did not effect LV/body wt in 1 or 2 copy mice, but increased LV/body wt 41% in 0 copy mice. We conclude that absent expression of NPR-A worsens right ventricular hypertrophy and causes left ventricular hypertrophy during exposure to chronic hypoxia without increasing pulmonary or systemic arterial pressure responses.

Continuous haemodynamic monitoring during withdrawal of diuretics in patients with congestive heart failure

AIMS

Right heart pressure parameters can be recorded continuously with the help of an implanted haemodynamic monitor. The aim of this study was to investigate the usefulness of the device in adjusting diuretic medication in patients with chronic congestive heart failure, and to evaluate the response of right ventricular pressure to increased volume load induced by diuretic withdrawal.

METHODS AND RESULTS

Four patients with stable congestive heart failure were implanted with an implantable haemodynamic monitor. Furosemide, the only diuretic used, was reduced by 50% the first week, withdrawn completely for the second week and then reinstituted in the initial dose. Right ventricular systolic and diastolic pressure, pulse pressure, dP/dt, estimated diastolic pulmonary artery pressure and heart rate were sampled continuously. Patients were evaluated by body weight, NYHA class, serum creatinine, serum brain natriuretic peptide, the 6 min walk test, quality of life and echocardiography on days 0, 7, 14 and 21. We observed significant changes in right ventricular pressure parameters in parallel with clinical signs and symptoms of worsening heart failure, such as increased body weight, a shorter walking distance and impaired quality of life. Moreover elevated levels of brain natriuretic peptide and lower creatinine levels were observed.

CONCLUSION

Haemodynamic changes due to increased volume load can be detected with an implantable haemodynamic monitor. Such data provide useful information for tailoring an optimal diuretic dose in patients with congestive heart failure.

[Pulmonary hemodynamics and right ventricular function]

Measurement of continuous blood flow by thermodilution catheter takes into account measures that are intermittent, though the estimation of mean pressures is satisfactory. Natural pulsatile pulmonary circulation would remain unknown. To evaluate pulsatile pulmonary hemodynamics and its importance in right ventricular function, the calculation of impedance based on spectral analysis of pressure and flow waves would allow their respective contributions to resistance, elastance and wave reflection upon after right ventricle loading. Computerization allows bedside monitoring of this sophisticated assessment of right ventricle after loading.

Ventriculo-vascular interaction in the normal development of the fetal circulation

OBJECTIVES

To examine cardiovascular physiology in the healthy fetus during normal development.

DESIGN

Twenty normal fetuses were studied longitudinally from 20 weeks to term. Serial echocardiography was performed, and arterial and venous diameter pulse wave characteristics and aortic pulse wave propagation velocity (PWV) were examined in the thoracic descending aorta (AoD) and inferior caval vein (IVC) using an ultrasonic phase-locked echo-tracking system. Statistical analyses included ANOVA, paired t-test and logistic regression where appropriate.

RESULTS

Aortic PWV, maximum incremental and late decremental velocities increased with gestation while the relative pulse amplitude decreased, reflecting falling distal impedance. There was a linear increase in cardiac preload and relative pulse amplitude in the IVC with gestation that correlated significantly with the presence of end-diastolic flow in the pulmonary artery and improvement in right ventricular diastolic function.

CONCLUSIONS

Non-invasive concurrent assessment of preload, ventricular function and impedance are possible in the fetus and may prove useful in the longitudinal study of fetal adaptation to pathophysiological changes.

Hemodynamic changes with right lateral decubitus body positioning in the tilted porcine heart

BACKGROUND

In beating-heart coronary surgical procedures, exposure of posterior vessels through sternotomy causes cardiac function to deteriorate. We hypothesized that turning the subject to the right lateral decubitus position before cardiac retraction improves exposure of posterior vessels and preserves cardiac pump function on displacement.

METHODS

Eight 80-kg open-chest pigs were instrumented with catheter-tip manometers. After a stepwise 60-degree turn to the right lateral decubitus position of the body, the heart was retracted anteriorly to 90 degrees with a suction stabilizer.

RESULTS

Right lateral body positioning caused an approximately 45-degree right deviation of the apex, thereby exposing the left atrial groove. Stroke volume, mean arterial pressure, right atrial pressure, and right ventricular end-diastolic pressure increased to 106% +/- 5% (mean +/- standard error of the mean, p = 0.31), 106% +/- 3% (p = 0.01), 129% +/- 8% (p = 0.001), and 171% +/- 14% (p = 0.002), respectively, compared with control values. In contrast, left atrial pressure decreased to 73% +/- 6% (p = 0.007), whereas left ventricular preload remained unchanged (110% +/- 8%, p = 0.26). Additional anterior displacement to 90 degrees fully exposed the posterior vessels, and stroke volume decreased to 90% +/- 3% (p = 0.01) and mean arterial pressure to 93% +/- 5% (p = 0.07) at the expense of further increased right ventricular preload (256% +/- 28%, p < 0.001).

CONCLUSIONS

By placing the subject in the right lateral decubitus position, exposure through sternotomy of posterior vessels in the beating porcine heart was facilitated while mean arterial pressure was maintained.

An artificial lung reduces pulmonary impedance and improves right ventricular efficiency in pulmonary hypertension

OBJECTIVE

Artificial lungs may have a role in supporting patients with end-stage lung disease as a bridge or alternative to lung transplantation. This investigation was performed to determine the effect of an artificial lung, perfused by the right ventricle in parallel with the pulmonary circulation, on indices of right ventricular load in a model of pulmonary hypertension.

METHODS

Seven adult male sheep were connected to a low-resistance membrane oxygenator through conduits anastomosed end to side to the pulmonary artery and left atrium. Banding of the distal pulmonary artery generated acute pulmonary hypertension. Data were obtained with and without flow through the device conduits. Outcome measures of right ventricular load included hemodynamic parameters, as well as analysis of impedance, power consumption, wave reflections, cardiac efficiency, and the tension-time index.

RESULTS

The model of pulmonary hypertension increased all indices of right ventricular load and decreased ventricular efficiency. Allowing flow through the artificial lung significantly reduced mean pulmonary artery pressure, zero harmonic impedance, right ventricular power consumption, amplitude of reflected waves, and the tension-time index. Cardiac efficiency was significantly increased.

CONCLUSIONS

An artificial lung perfused by the right ventricle and applied in parallel with the pulmonary circulation reduces ventricular load and improves cardiac efficiency in the setting of pulmonary hypertension. These data suggest that an artificial lung in this configuration may benefit patients with end-stage lung disease and pulmonary hypertension with right ventricular strain.

Electroanatomic mapping of arrhythmogenic right ventricular dysplasia

OBJECTIVES

We tested the hypothesis that spatial association of low-amplitude intracardiac electrograms can identify the presence, location and extent of dysplastic regions in arrhythmogenic right ventricular dysplasia (ARVD).

BACKGROUND

Arrhythmogenic right ventricular dysplasia is a right ventricular (RV) cardiomyopathy characterized pathologically by fibrofatty infiltration and clinically by a spectrum of arrhythmias, sudden cardiac death and RV failure. Diagnosis of ARVD still remains a clinical challenge.

METHODS

A three-dimensional electroanatomic mapping technique was used to map the RV of two groups of patients: 1) those with ARVD presenting with typical clinical, electrocardiographic and echocardiographic or magnetic resonance imaging (MRI) findings; and 2) those with structurally normal ventricles.

RESULTS

The dysfunctional RV area could be identified only in the first group and was characterized by the presence of discrete areas of abnormally low-amplitude electrograms. Hence, the normal voltage values observed in the control group (unipolar: 11.9 +/- 0.3 mV; bipolar: 4.6 +/- 0.2 mV [mean +/- SEM]) and in the nonaffected zones in the ARVD group (unipolar: 10.4 +/- 0.2 mV; bipolar: 4.6 +/- 0.2 mV) were reduced significantly (p < 0.05) in the dysplastic areas (unipolar: 3.3 +/- 0.1 mV; bipolar: 0.5 +/- 0.1 mV). The pathologic process mainly involved the RV anterolateral free wall, apex and inflow and outflow tracts and ranged from patchy areas to uniform and extensive involvement. Concordance between electroanatomic findings and MRI or echocardiographic findings was noted in all patients.

CONCLUSIONS

The pathologic substrate in ARVD can be identified by spatial association of low-amplitude endocardial electrograms, reflecting replaced myocardial tissue. The ability to accurately identify the presence, location and extent of the pathologic substrate may have important diagnostic, prognostic and therapeutic implications.

Paradoxic abbreviation of repolarization in epicardium of the right ventricular outflow tract during augmentation of Brugada-type ST segment elevation

We report the case of a 53-year-old Japanese man with a typical Brugada-like ECG in whom epicardial and endocardial activation-recovery intervals (ARI) in the right ventricular outflow tract (RVOT) were simultaneously measured by recording unipolar electrograms from the Pathfinder catheter introduced in the great cardiac vein as well as from the multielectrode basket catheter deployed in the RVOT. Epicardial ARI in the RVOT was abbreviated paradoxically at the beat of augmented ST segment elevation in lead V2 after a long pause or after pilsicainide injection. Endocardial ARI in the RVOT and epicardial ARI in the left ventricle were prolonged or were not changed. Our data support the hypothesis that heterogenous response of repolarization across the ventricular wall in the RVOT is responsible for accentuation of ST segment elevation in the right precordial leads.

Usefulness of Doppler tissue imaging for the assessment of right and left ventricular myocardial function in patients with dual-chamber pacing

The aim of the study was to evaluate by Doppler tissue imaging (DTI) the combined effects of atrio-ventricular (AV) delay and heart rate (HR) changes on global and segmental right (RV) and left (LV) ventricular diastolic function in 15 patients with dual-chamber pacemakers paced in the DDD mode. RV and LV inflow velocities and regional systolic and diastolic pulsed-wave (PW) DTI parameters were analyzed at four different pacing modes: (1) HR 70 beats/min, AV delay 125 ms; (2) HR 70 beats/min, AV delay 188 ms; (3) HR 89 beats/min, AV delay 125 ms; (4) HR 89 beats/min, AV delay 188 ms. For each pacing mode selected, RV diastolic filling velocities always prevailed over LV ones. As for RV and LV adaptation to the four different stimulation protocols, a higher paced rate and a prolonged AV delay caused across both the AV valves a decrease of E wave and of E/A ratios. The intersegmental comparison of PW-DTI parameters outlined that RV free wall exhibited significantly higher peak systolic (Sm) and early-diastolic (Em) wall velocities, and longer systolic ejection time. Considering separately RV and LV segmental physiology at the four programmed pacing modes, an increase in HR determined a progressive shortening of systolic ejection times in all the segments analyzed. Moreover, in each region the Em/Am ratio decreased with higher HR and longer AV delay. Conversely, Em encountered a progressive reduction in RV free wall, while remaining quite unchanged in all the LV regions. Both ventricles shared a similar pattern of global and regional adaptation to programmed HR and AV delay modifications, consisting in a progressive greater contribution of late diastole to ventricular filling at higher HR and more prolonged AV delay. However, at a regional level the right ventricle exhibited higher systolic and diastolic wall velocities than all left ventricular regions.

Quantification of aortic regurgitation by real-time 3-dimensional echocardiography in a chronic animal model: computation of aortic regurgitant volume as the difference between left and right ventricular stroke volumes

BACKGROUND

The accuracy of conventional 2-dimensional echocardiographic and Doppler techniques for the quantification of valvular regurgitation remains controversial. In this study, we examined the ability of real-time 3-dimensional (RT3D) echocardiography to quantify aortic regurgitation by computing aortic regurgitant volume as the difference between 3D echocardiographic-determined left and right ventricular stroke volumes in a chronic animal model.

METHODS

Three to 6 months before the study, 6 sheep underwent surgical incision of one aortic valve cusp to create aortic regurgitation. During the subsequent open chest study session, a total of 25 different steady-state hemodynamic conditions were examined. Electromagnetic (EM) flow probes were placed around the main pulmonary artery and ascending aorta and balanced against each other to provide reference right and left ventricular stroke volume (RVSV and LVSV) data. RT3D imaging was performed by epicardial placement of a matrix array transducer on the volumetric ultrasound system, originally developed at the Duke University Center for Emerging Cardiovascular Technology. During each hemodynamic steady state, the left and right ventricles were scanned in rapid succession and digitized image loops stored for subsequent measurement of end-diastolic and end-systolic volumes. Left and right ventricular stroke volumes and aortic regurgitant volumes were then calculated and compared with reference EM-derived values.

RESULTS

There was good correlation between RT3D left and right ventricular stroke volumes and reference data (r = 0.83, y = 0.94x + 2.6, SEE = 9.86 mL and r = 0.63, y = 0.8x - 1.0, SEE = 5.37 mL, respectively). The resulting correlation between 3D- and EM-derived aortic regurgitant volumes was at an intermediate level between that for LVSV and that for RVSV (r = 0.80, y = 0.88x + 7.9, SEE = 10.48 mL). RT3D tended to underestimate RVSV (mean difference -4.7 +/- 5.4 mL per beat, compared with -0.03 +/- 9.7 mL per beat for the left ventricle). There was therefore a small overestimation of aortic regurgitant volume (4.7 +/- 10.4 mL per beat).

CONCLUSION

Quantification of aortic regurgitation through the computation of ventricular stroke volumes by RT3D is feasible and shows good correlation with reference flow data. This method should also be applicable to the quantification of other valvular lesions or single site intracardiac shunts where a difference between right and left ventricular cavity stroke volumes is produced.

Normal human right and left ventricular mass, systolic function, and gender differences by cine magnetic resonance imaging

Our objective was to establish normal ranges of left and right ventricular mass and function with cine magnetic resonance imaging (MRI) and to determine gender differences. Seventy-five healthy subjects (age range 8-55, mean 28 yr) were studied with cine MRI. Ten dogs were imaged for autopsy validation with a mean difference between actual and MRI-determined mass of 0.2 A +/- 8.4 g. Intraobserver and interobserver variability and interstudy variability were 5-6%. All parameters were significantly different between males and females except ejection fraction and the left ventricular mass to end-diastolic volume ratio. Agreement with published autopsy series, including gender differences, was excellent. This study presents normative MRI data that can be used for comparing individual patients and for further study of right and left ventricular interaction.

Comparative evaluation of thermodilution and gated blood pool method for determination of right ventricular ejection fraction at rest and during exercise

BACKGROUND

Since the development of a Swan-Ganz thermodilution ejection fraction catheter several studies have been published which compare this technique for obtaining right ventricular ejection fraction (RVEF(TD)) with alternative methods. However, the reliability of RVEF(TD) measurements under exercise conditions remains undetermined. Therefore, the aim of the present study was a comparative evaluation of RVEF(TD) with the established gated blood pool method (RVEF(GBP)) under exercise conditions.

METHODS AND RESULTS

Twenty-two patients with different cardiac diseases underwent right heart catheterization, including RVEF(TD) and simultaneous RVEF(GBP) determination at rest and during supine bicycle exercise. Linear regression analysis showed a significant correlation between RVEF(TD) and RVEF(GBP) at rest (r = 0.73, p < or = 0.0005) and during exercise (r = 0.74, p < or = 0.0005). A Wilcoxon analysis showed a high probability of agreement of RVEF(TD) and RVEF(GBP) at rest and exercise (level of significance for error of the 0 hypothesis of 95.9/73.3%).

CONCLUSION

The thermodilution ejection fraction catheter provides a useful device for reliable, repetitive and safe RVEF measurements, not only at rest but also under exercise conditions. This seems to be clinically important, because by it means RVEF, as a sensitive parameter of primary or secondary right ventricular dysfunction, can be determined in the course of standard right heart catheterization.

The structure and function of the helical heart and its buttress wrapping. VII. Critical importance of septum for right ventricular function

The macroscopic structure of the right ventricle includes a transverse basal loop for the free wall, and oblique septal components, originating from the descending and ascending segments of the apical loop. Data is presented that determines why right ventricular function is related principally to intraventricular septal function, and why right ventricular failure is magnified by septal stunning caused by poor myocardial protection. The background of this architectural/functional change can explain normal right ventricular function, the relationship of right ventricular performance to pulmonary vascular resistance, experimental studies that characterize right ventricular performance after architectural free wall ablation, right ventricular disconnection, right coronary occlusion, and free wall replacement. These basic science studies are related to perioperative right ventricular performance, involving methods of myocardial protection, protamine reaction, right coronary occlusion and reperfusion, right ventricular dyskinesia, chronic aortic and mitral valve replacement (MVR) replacement, congenital heart disease, right and left ventricular assist devices (LVADs), and transplantation. The predominant focus is related to the septum and how it can be evaluated perioperatively. Septal evaluation by echocardiogram should become an essential feature during intraoperative management.

Magnetic resonance imaging of stentless xenografts for reconstruction of right ventricular outflow tract

The objective was to overcome allograft shortage during the Ross operation; stentless xenografts were carefully evaluated for hemodynamic behavior and valve deterioration during medium term follow-up. Between January 10, 1994 and January 4, 1996 nine adult patients (age 31-51 years) underwent aortic valve replacement with an autologous pulmonary valve and right ventricular outflow tract reconstruction with the Edwards Prima or Medtronic Freestyle xenograft. One patient was dead early and one late, both from noncardiac reasons. Forty-eight to 66 months follow-up was available for 7 patients and was performed with physical examination in the outpatient clinic, transthoracic echocardiography (TTE), and magnetic resonance imaging (MRI). Two patients received 29-mm valves and the remaining 27-mm valves. No reoperation became necessary during follow-up. Preoperative left ventricular ejection fraction ranged from 20% to 84%, median 61%, mean 59% +/- 18%. At latest follow-up left ventricular ejection fraction was 49% to 70%, median 57%, mean 58% +/- 8%. TTE showed no calcification of the xenograft wall or cusps. MRI revealed good autograft function with no evidence of stenosis in any patient. Four patients showed no and three trivial regurgitation. Right ventricular outflow tract-stenosis could not be seen in any patient. Calculated gradients of the xenograft valves ranged from 2 to 6 mm Hg, median 3 mm Hg (mean 3.1 +/- 2.4 mm Hg) and calculated EOA ranged from 2.0 to 4.0 cm(2), median 2.8 cm(2). MRI supported these findings and showed pliable xenograft cusps in all patients. Right ventricular function was well preserved in all patients. In adult patients right ventricular outflow tract reconstruction with stentless xenografts can be performed safely and intermediate-term results are encouraging. During medium-term (5-7 years) follow-up no calcification or deterioration of valve function occurred with excellent hemodynamic behavior.

Comparison of changes in hemodynamics between unilateral and bilateral lung volume reduction for pulmonary emphysema

This study was aimed to compare changes in hemodynamics between unilateral (UL) or simultaneous bilateral (BL) lung volume reduction surgery (LVRS) for chronic obstructive lung disease. Sixteen patients underwent LVRS by stapler resection with neodymium: yttrium-alminum-garnet (Nd: YAG) laser ablation; five underwent BL-LVRS (four by median sternotomy and one by thoracoscopy) and 11 underwent UL-LVRS by thoracoscopy. Four patients had multiple bullae within pulmonary emphysema. At preoperation and 6, 12, 24, and 48 hours postoperatively, hemodynamics and right ventricular performance were evaluated. UL- and BL-LVRS reduced afterload of the right and left ventricle postoperatively. Although the pulmonary arterial resistance increased after surgery, the total pulmonary resistance decreased (p=0.001) in association with the reduced systemic vascular resistance (p=0.001). These reductions improved cardiopulmonary circulation, resulting in increased stroke volume and cardiac output (p=0.003). The right ventricular ejection fraction showed minimal change 48 hours postoperation. Two patients died of pneumonia caused by persistent air leakage. In conclusion, both the UL- and BL-LVRS showed similar effectiveness in terms of improvement in the systemic and cardiopulmonary circulation after LVRS, if there were no postoperative complications. We concluded that we had to reduce and repair the persistent air leakage after LVRS.

A new percutaneously adjustable, thoracoscopically implantable, pulmonary artery banding: an experimental study

BACKGROUND

In patients who undergo left ventricular retraining, multiple reoperations are often necessary to adjust the pulmonary artery banding. The availability of a percutaneously adjustable band would be very useful.

METHODS

Ten lambs (10 to 25 kg) underwent pulmonary artery banding using a new device, 7 by thoracotomy and 3 by thoracoscopy. The possibility of percutaneously adjusting the band was evaluated immediately after operation in 10 animals and at 3 months in 8 animals.

RESULTS

One death occurred on the day of the procedure from displacement of the device and another death was from infection. Immediate hemodynamic studies proved the feasibility of increasing right ventricular afterload in a precise and reversible way. After 3 months the band could still be precisely loosened or tightened in all but 1 animal. Autopsy revealed that all the devices were in the correct position and no fibrosis or adhesions were present around the devices, and there was no residual stenosis noted on the pulmonary artery.

CONCLUSIONS

This new device may be a valuable alternative to the repeated pulmonary artery banding needed for ventricular preparation.

Transient pleural effusion in norepinephrine-stimulated rats

Transient pleural effusions occurred in rats receiving continuous intravenous infusion of norepinephrine (NE, 0.1 mg/kg/h). We hypothesized that these pleural effusions result from a NE-induced increase in right ventricular systolic pressure (RVSP) and total peripheral resistance (TPR). NE was administered over time intervals between 20 min and 72 h. It induced an immediate doubling in RVSP whereas LVSP remained at the control level. TPR increased with a delay of 6 h. At this time, pleural effusions occurred in NE-treated animals, reached their maximum after 8h and disappeared after 24 h of NE stimulation. Combining NE with the alpha-blocker prazosin normalized TPR and prevented pleural effusions. Therefore, we interpret the pleural effusion as a consequence of pulmonary venous congestion, mainly caused by an increased TPR. LV hypertrophy which developed after 24 h of NE stimulation is considered to compensate for the hemodynamic disturbance due to the NE-induced elevation in TPR. This is reflected in the disappearance of pleural effusion.

Influence of cyclic variation of right ventricular volume on left ventricular mechanical parameters measured with conductance catheter

The conductance catheter is widely used for the continuous measurement of the left ventricular (LV) pressure-volume loops. Cyclical change of the right ventricular (RV) volume may alter the parallel conductance volume, thereby affecting the LV mechanical parameters. Using 8 open-chest adult mongrel dogs, multiple LV pressure-volume loops were obtained by 2 methods: first with a vena cava occlusion (VCO) method, which involved RV volume alteration, and second with a right-heart-bypass (RHB) preparation, which decompressed the right ventricle completely. The slope of the end-systolic pressure-volume relation (Ees), the end-systolic volume associated with the end-systolic pressure of 100 mmHg (V100,es), stiffness constant (beta), and the end-diastolic volume associated with the end-diastolic pressure of 9 mmHg (V9,ed) were calculated from each loop. There was minimal influence from RV volume alteration on systolic-phase indices [Ees (VCO method, 6.37 +/- 1.91 mmHg/ml; RHB preparation, 6.60 +/- 1.66mmHg/ml; p=0.356), and V100,es (VCO method, 18.4 +/- 9.3ml; RHB preparation, 17.8 +/- 9.0 ml; p=0.681)], but there was a significant influence on diastolic-phase indices [beta (VCO method, 0.0599 +/- 0.0152; RHB preparation, 0.0839 +/- 0.0150; p=0.007), and V9,ed (VCO method, 35.6 +/- 11.3 ml; RHB preparation, 31.9 +/- 12.3 ml; p=0.001)]. The increase in the RV volume in the diastolic phase increased the parallel conductance volume, causing overestimation of the LV diastolic volume measured by the conductance catheter.

Echocardiographic evaluation of left and right ventricular function in mild hypertension

Thirty-one cases of untreated 'mild hypertension' and equal number of age and sex matched controls with 'normal' blood pressure were evaluated by echocardiography. Patients with mild hypertension had significantly increased left ventricular mass index, concentric remodeling, and diastolic dysfunction. Thickness of right ventricular anterior wall, flow velocities across tricuspid and pulmonary valves were also significantly higher in hypertensives. Pulmonary flow acceleration time was significantly less in hypertensives. On multiple regression analysis, mitral valve 'A' wave velocity alone correlated with systolic blood pressure. Other echocardiographic variables did not have any relation with blood pressure readings. Height, weight, body surface area and body mass index could also explain only around 50% of variability in echocardiographic parameters. Cardiac structure and functions in hypertensives are affected by factors other than blood pressure reading, body surface area or body mass index. Routine echocardiography can be useful in identifying those patients of mild hypertension who have disproportionate increase in left ventricular mass or disproportionate impairment of diastolic functions.

[Synchronization of the contraction of the right ventricle against an acute afterload increase. Left ventricle-like mechanical function of the right ventricle]

AIM

The aim of this study was to demonstrate right ventricular contraction synchronization during acute and moderate afterload increase.

MATERIAL AND METHOD

Right and left ventricular pressures, pulmonary and aortic pressures, pulmonary flow, and ventricular volumes by sonomicrometry were measured in seven anesthetized sheep. Pulmonary arterial hypertension was induced by Escherichia coli endotoxemia.

RESULTS

Acute increase of the right ventricular afterload, measured as the mean arterial pulmonary pressure (11.9 1.3 to 24 3.6 mmHg) produced the following changes in the right ventricle without preload and contractility changes: a) maximal elastance shifted towards the end of the ejection (127.5 18.5 ms) and the ejection time shortened (57.5 20.3 ms), so that the negative peak of the first ventricular pressure derivative occurred at the end of the ejection; b) the pressure-volume loop became rectangular, i.e.; the systolic and diastolic phases were isovolumic, and c) the ejection showed a single phase.

CONCLUSIONS

Asynchronous and sequential right ventricular contraction with normal afterload changed to a synchronic contraction pattern as in the left ventricle during an acute and moderate afterload increase. This left ventricle-like mechanical property establishes a novel mechanical reserve mechanism of the right heart, since it allows the right ventricle to maintain its systolic function during an afterload increase, independently of the preload and contractility.

Evaluation of right ventricular performance with a right ventricular ejection fraction thermodilution catheter and MRI in patients with pulmonary hypertension

STUDY OBJECTIVES

We sought to compare catheter studies using a right ventricular ejection fraction (REF) catheter together with echocardiography and MRI in patients with pulmonary hypertension.

PATIENTS AND METHODS

We compared hemodynamic findings, echocardiography, and MRI studies in 16 patients with pulmonary hypertension. Six healthy volunteers served as control subjects for the MRI studies.

RESULTS

MRI imaging provided accurate assessment of cardiac output in all but two patients. As compared with MRI, the REF catheter constantly underestimated the REF and overestimated right ventricular volumes in patients with pulmonary hypertension. REF, end-systolic and end-diastolic right ventricular volumes, and right ventricular muscle mass, as determined by MRI, were almost identical in patients with preserved cardiac function and those with low-output failure. The only factor that was different in both groups was the severity of tricuspid regurgitation.

CONCLUSION

Right ventricular dimensions and muscle mass do not differ in patients with pulmonary hypertension who have low cardiac output and those who do not. According to our results, the major determinant of cardiac output in these patients appears to be the severity of tricuspid regurgitation. The REF catheter provides invalid data on right ventricular dimensions in patients with pulmonary hypertension.

Pro-atrial natriuretic peptide hormone from right atria is correlated with cardiac depression in septic patients

N-terminal pro-atrial natriuretic peptide [proANP(1-98)] has been extensively investigated in patients with chronic heart failure and ishemic heart disease. It is found to be a better marker of cardiac dysfunction than atrial natriuretic peptide (ANP). The possible involvement of proANP(1-98) in cardiac depression caused by sepsis has not been studied yet. Therefore, we analyzed atrial plasma concentration of proANP(1-98) in 17 septic patients with hemodynamic variables measured or calculated using pulmonary artery catheter. The results of altogether 96 measurements show a significant negative correlation of proANP(1-98) and cardiac index (p<0.024), oxygen delivery (p<0.03) and oxygen consumption (p<0.03). There is also a positive correlation with pulmonary vascular resistance (p<0.03). ProANP(1-98) is significantly higher in patients who developed acute respiratory distress syndrome (ARDS) (p<0.001). This study implies that proANP(1-98) is a possible novel hormone marker of cardiac depression caused by sepsis that could be used for prediction of ARDS.

Quantitative echocardiographic assessment of the performance of the functionally single right ventricle after the Fontan operation

BACKGROUND

Performance of the functionally single right ventricle may deteriorate over time. Quantitative assessment of this chamber, however, is complicated by its asymmetric geometry. Automatic detection of borders, and the Doppler-derived index of myocardial performance, are echocardiographic techniques that allow for quantitative assessment regardless of ventricular shape. We sought to evaluate the mechanics of contraction and relaxation in the functionally single right ventricle using these parameters.

METHODS

We evaluated systemic ventricular function in 35 asymptomatic patients with functionally single right ventricle, having a mean age of 7.8+/-3.1 years, who had undergone the Fontan procedure. We compared them with 32 age-matched normal controls using both automatic detection of borders and Doppler indexes.

RESULTS

When compared with the controls, the group with a functionally single right ventricle demonstrated diminished systolic function as evidenced by a lower fractional change in area (42.7+/-10.1% vs. 54.6+/-10.5%, p = 0.001), and diminished diastolic function, as demonstrated by a greater reliance on atrial contraction to achieve ventricular filling (32.0+/-4.4% vs. 22.2+/-4.1%, p = 0.001). The mean index of myocardial performance in those with functionally single right ventricles was also greater than in controls (0.41+/-0.12 vs. 0.30+/-0.05, p = 0.001), and the indexed ejection time was shorter (0.35+/-0.05 vs. 0.39+/-0.05, p = 0.01), suggesting less efficient ventricular mechanics.

CONCLUSIONS

These data demonstrate that the systolic and diastolic properties of the functionally single right ventricle differ significantly from those of the normal systemic left ventricle. Use of the echocardiographic techniques provide insight into ventricular mechanics in patients with functionally single ventricles, and may be valuable tools for serial quantitative follow-up.