Effects of inhaled nitric oxide on right ventricular function in severe acute respiratory distress syndrome

Objective To compare the effects of inhaled nitric oxide (NO) and an infusion of prostacyclin (PGI₂) on right ventricular function in patients with severe acute respiratory distress syndrome (ARDS).Design Randomized prospective short-term study.Setting: Post-surgical ICU in an university hospital.Patients 10 patients with severe ARDS referred to our hospital for intensive care.Interventions In random sequence the patients inhaled NO at a concentration of 18 parts per million (ppm) followed by 36 ppm, and received an intravenous infusion of PGI₂ (4 ng·kg^–1·min^–1).Measurement and results Inhalation of 18 ppm NO reduced the means (±SE) pulmonary artery pressure (PAP) from 33±2 to 28±1 mmHg (p=0.008), increased right ventricular ejection fraction (RVEF), as assessed by thermodilution technique, from 28±2 to 32±2% (p=0.005), decreased right ventricular end-diastolic volume index from 114±6 to 103±8 ml·m^–2 (p=0.005) and right ventricular end-systolic volume index from 82±4 to 70±5 ml·m^–2 (p=0.009). Mean arterial pressure (MAP) and cardiac index (CI) did not change significantly. The effects of 36 ppm NO were not different from the effects of 18 ppm NO. Infusion of PGI₂ reduced PAP from 34±2 to 30±2 mmHg (p=0.02), increased RVEF from 29±2 to 32±2% (p=0.02). Right ventricular end-diastolic and end-systolic volume indices did not change significantly. MAP decreased from 80±4 to 70±5 mmHg (p=0.03), and CI increased from 4.0±0.5 to 4.5±0.5 l·min^–1·m^–2 (p=0.02).Conclusions Using a new approach to selective pulmonary vasodilation by inhalation of NO, we demonstrate in this groups of ARDS patients that an increase in RVEF is not necessarily associated with a rise in CI. The increase in CI during PGI₂ infusion is probably related to the systemic effect of this substance.Supported by DFG Fa 139/1-2/2-2     

Influence of constant sustained positive airway pressure on right ventricular performance

Objective The detrimental effect of positive airway pressure on right ventricular (RV) performance is controversial and the aim of this study was to determine the effects of constant positive airway pressure without ventilatory fluctuation on RV performance with the aid of a pulmonary arterial catheter equipped with a rapid response thermistor for measuring RV ejection fraction (RVEF) and RV end-diastolic volume index (RVEDVI).Design A prospective, clinical study.Setting The central operating theatre of a university hospital.Patients Nine patients who had major surgery and required right heart catheterization for normal clinical management.Measurements and results Cold indicator was injected into the RV 4 or 5 times for each airway pressure (0, 10 or 20 cmH₂O) which was maintained manually stable for 15 s, and 9 paired data were analyzed by repeated-measures analysis of variance. They are separated into two groups; RVEF at zero airway pressure greater (A group) or less (B group) than 0.4. In A group (7 patients), increasing airway pressures (0 vs 10 vs 20 cmH₂O) did not affect RVEF (0.55±0.05 vs 0.54±0.06 vs 0.56±0.04), RVEDVI (69±36 vs 73±29 vs 58±20 ml·m^–2), or stroke volume index (SVI: 38±18 vs 40±17 vs 33±13 ml·beat^–1 ·m^–2); however, in B (2 patients), RVEF (0.35 and 0.38 vs 0.31 and 0.28 vs 0.19 and 0.17) and SVI (35 and 28 vs 32 and 27 vs 27 and 23) decreased, while RVEDVI increased (99 and 73 vs 103 and 97 vs 146 and 132).Conclusions In most patients, the changes in RVEF, SVI, and RVEDVI did not occur under constant positive airway pressure, therefore the changes reported in mechanically ventilated patients may not attributable to the extent of positive airway pressure but rather to abrupt increases in airway pressure. There appears, however, to be patients whose RV function is so disturbed that they cannot cope with increased afterloads.     

Effects of norepinephrine on right ventricular function in septic shock patients

Objective To study the effects of norepinephrine on right ventricular function in patients with hyperdynamic septic shock.Design Prospective, open study.Setting A 15 bed ICU in a university hospital.Patients 9 patients with hyperdynamic septic shock (SBP<90 mmHg, Cl4l·min^–1·m^–2, SVRI850 dynes·s·cm^–5m^–2 and oliguria).Interventions Plasma volume expansion was used to correct a suspected volume deficit and then, norepinephrine infusion was started and titrated to restore systemic blood pressure to the normal range (mean infusion rate: 1.1±0.2 mcg·kg^–1·min^–1). Norepinephrine was the only vasoactive agent used in these patients.Measurements and results A modified Swan-Ganz catheter mounted with a fast response thermistor was inserted in each patient, allowing repeated measurements of RVEDVI and RVEF. At time of inclusion to the study, all but one patient had elevated MPAP (23±4 mmHg) and RVEF50%, and all patients had RVEDVI90 ml·m^–2. During norepinephrine infusion, MAP increased from 51±9 to 89±10 mmHg (p<0.0001), PVRI increased from 204±35 to 286±63 dynes·s·cm^–5·m^–2 (p<0.05), and despite this increase in right ventricular afterload, no detrimental effect in RVEF (36±11 to 36±10%) or in RVEDVI (116±30 to 127±40 ml·m^–2) was observed. A Frank-Starling relationship for the right ventricle was constructed by plotting an index of ventricular performance (RVSWI) against an index of ventricular preload (RVEDVI). A significant upward shift to the right of the relationship was observed during norepinephrine infusion.Conclusion It was concluded that norepinephrine exerted a favourable effect on right ventricular function.Work done at Sainte Marguerite Hospital, Marseille, France     

Prognostic value of cardiovascular magnetic resonance derived right ventricular function in patients with interstitial lung disease

Background

Cardiovascular magnetic resonance (CMR) provides non-invasive and more accurate assessment of right ventricular (RV) function in comparison to echocardiography. Recent study demonstrated that assessment of RV function by echocardiography was an independent predictor for mortality in patients with interstitial lung disease (ILD). The purpose of this study was to determine the prognostic significance of CMR derived RV ejection fraction (RVEF) in ILD patients.

Methods

We enrolled 76 patients with ILD and 24 controls in the current study. By using 1.5 T CMR scanner equipped with 32 channel cardiac coils, we performed steady-state free precession cine CMR to assess the RVEF. RV systolic dysfunction (RVSD) was defined as RVEF ≤45.0% calculated by long axis slices. Pulmonary hypertension (PH) was defined as mean pulmonary artery pressure (mPAP) of more than 25 mmHg at rest in the setting of pulmonary capillary wedge pressure ≤15 mmHg.

Results

The median RVEF was 59.2% in controls (n = 24), 53.8% in ILD patients without PH (n = 42) and 43.1% in ILD patients with PH (n = 13) (p < 0.001 by one-way ANOVA). During a mean follow-up of 386 days, 18 patients with RVSD had 11 severe events (3 deaths, 3 right heart failure, 3 exacerbation of dyspnea requiring oxygen, 2 pneumonia requiring hospitalization). In contrast, only 2 exacerbation of dyspnea requiring oxygen were observed in 58 patients without RVSD. Multivariate Cox regression analysis showed that RVEF independently predicted future events, after adjusting for age, sex and RVFAC by echocardiography (hazard ratio: 0.889, 95% confidence interval: 0.809 – 0.976, p = 0.014).

Conclusions

The current study demonstrated that RVSD in ILD patients can be clearly detected by cine CMR. Importantly, low prevalence of PH (17%) indicated that population included many mild ILD patients. CMR derived RVEF might be useful for the risk stratification and clinical management of ILD patients.     

Splanchnic oxygen transport after cardiac surgery: evidence for inadequate tissue perfusion after stabilization of hemodynamics

Objective To evaluate the adequacy of visceral oxygen transport and gastric pH_i after open heart surgery in patients with stable hemodynamics.Design Nonrandomized control trial.Setting A general intensive care unit in a tertiary care center.Patients Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics.Interventions The effect of dobutamine infusion (6 g kg^–1 min^–1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pH_i by gastric tonometer.Measurements and results Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2±0.6 vs 4.4±0.7l· min^–1·m^–2;P<0.05), splanchnic blood flow (0.68±0.28 vs 0.91±0.281· min^–1·m^–2;p<0.05) and femoral blood flow (0.25±0.08 vs 0.32±0.11l·min^–1·m^–2;p<0.05). Changes in splanchnic oxygen delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pH_i did not change (7.30±0.08 vs 7.31±0.06; NS), while in the control group, gastric pH_i tended to decrease (7.32±0.04 vs 7.28±0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141±11 vs 149±11 ml· min^–1·m^–2;P<0.05) but did not change in the control group.Conclusions We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.This study was supported in part by the senior researcher's grant no. 1945/3015/92 to Dr. Takala from the Academy of Finland     

Right ventricular myocardial function in ARF patients

Objective To examine the hemodynamic effects of external positive end-expiratory pressure (PEEP) on right ventricular (RV) function in acute respiratory failure (ARF) patients.Design Prospective, with retrospective analysis on the basis of RV volume response to PEEP.Setting General intensive care unit in a university teaching hospital.Patients 20 mechanically ventilated ARF patients (mean lung injury score=2.6±0.45 SD).Intervention Incremental levels of PEEP (0–5–10–15 cmH₂O) were applied and RV hemodynamics were studied by means of a Swan-Ganz catheter with a fast-response thermistor for right ventricular ejection fraction (RVEF) measurement. According to their response to PEEP 15, two groups of patients were defined: group A (9 patients) with unchanged or increased RV end-diastolic volume index (RVED-VI) and group B (11 patients) with decreased RVEDVI.Measurements and results At zero PEEP (ZEEP) the hemodynamic parameters of the two groups did not differ. In group A, cardiac index (CI) and stroke volume index (SI) decreased at all PEEP levels (5, 10, and 15 cmH₂O), while RVEF started to decrease only at a PEEP of 10 cmH₂O (–10.8%), and RVES(systolic)VI increased only at PEEP 15 cmH₂O (+21.5%). RVED-VI was not affected by PEEP. In group B, CI and SI decreased at all PEEP levels (5, 10, and 15 cmH₂O). Similarly, RVEDVI started to decrease at PEEP 5 cmH₂O, while RVESVI decreased only at PEEP 15 cmH₂O (–21.4%). RVEF was not affected by PEEP in this group. In each patient the slope of the relationship between RVEDVI and right ventricular stroke work index (RVSWI), expressing RV myocardial performance, was studied. This relationship was significant (no change in RV contractility) in 8 of 11 patients in group B and in only 2 patients in group A. In 4 patients in group A, PEEP shifted the RVSWI/RVEDVI ratio rightward in the plot, indicating a decrease in RV myocardial performance in these patients.Conclusions PEEP affects RV function in ARF patients. The decrease in cardiac output is more often associated with a preload decrease and no change in RV contractility. On the other hand, the finding of increased RV volumes with PEEP may be associated with a reduction in RV myocardial performance. Thus, these results suggest that assessment of RV function by PEEP and preload recruitable stroke work may disclose otherwise unpredictable alterations in RV function.Partially supported by Consiglio Nazionale delle Ricerche grant, Italy     

Monitoring of right ventricular function using a conventional slow response thermistor catheter

Objective To investigate whether determination of right ventricular end-diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF) can be performed with reasonable accuracy and reproducibility using a conventional slow response thermistor pulmonary artery catheter (CPAC) applying an adaptive algorithm.Design To study RVEDV and RVEF simultaneously with pulmonary artery catheters equipped with slow and fast response thermistors (FRPAC) under a broad range of cardiac output.Setting Laboratory of Institute of Experimental Surgery, Technical University.Animals 11 anaesthetised piglets.Interventions Hypovolemia (V–) was induced by withdrawal of blood up to 50 ml/kg, hypervolemia (V+) was produced by retransfusing blood and adding up to 30 ml/kg hydroxyethyl starch. In 5 animals in phases V–and V+ beta-adrenergic stimulation was achieved with dobutamine. Finally pulmonary artery hypertension was induced by infusion of small air bubbles.Measurements and results Cardiac output (CO), RVEDV and RVEF were determined simultaneously with FRPAC and CPAC placed in the same pulmonary artery branch. Measurements were repeated 8 times sequentially in steady state normovolemia. A total of 130 measurements could be analysed. The coefficient of variation was 6.7±4.2 for CO_(FRPAC) and 4.6±1.7% for CO_(CPAC); for RVEF it was 9.7±6.2% (FRPAC) and 9.9±3.9% (CPAC); for RVEDV it was 11.6±4.8% (FRPAC) and 8.54±3.2 (CPAC). Mean difference (bias) was 0.06±0.39 l/min for CO measured with both methods, 19±35 ml for RVEDV and –3.3±6.5% for RVEF. CO_(CPAC) displayed a strong correlation to CO_(FRPAC) (R=0.97,p=0.001) as well as RVEF (R for RVEF_(CPAC) versus RVEF_(FRPAC)=0.90,p=0.001). R for RVEDV_(CPAC) versus RVEDV_(FRPAC) was 0.67,p=0.001. We conclude that this animal study demonstrates good agreement between RVEF and RVEDV obtained with catheters equipped with a fast response thermistor or with a conventional slow response thermistor allowing accurate monitoring of right ventricular function with a conventional pulmonary artery catheter.Supported in part by grants from BMFT (grant number 0706908)     

Combination of inhaled nitric oxide and intravenous prostacyclin for successful treatment of severe pulmonary hypertension in a patient with acute respiratory distress syndrome

Objective: To investigate the combination of inhaled nitric oxide (iNO) and intravenously administered prostacyclin (i. v. PGI₂) in a patient with severe pulmonary hypertension and acute respiratory distress syndrome (ARDS). Design: Single case study. Setting: Intensive care unit of a university hospital. Methods: In an ARDS patient with severe pulmonary hypertension, gas exchange and hemodynamics were measured during combined treatment with iNO and i. v. PGI₂. On two subsequent days, a protocol consisting of four 20-min periods was performed: baseline, 10 ppm iNO, 10 ppm iNO plus 4 ng kg⁻¹ min⁻¹, and 4 ng kg⁻¹ min⁻¹ PGI₂ alone. At the end of each period hemodynamic and gas exchange data were obtained. Results: The combination of iNO and i. v. PGI₂ resulted in a marked decrease in pulmonary artery pressure and a concomitant increase in cardiac output which was more pronounced than the effect of either drug alone. During iNO, as well as during the combination of iNO and i. v. PGI₂, oxygenation was improved, whereas during i. v. PGI₂ alone oxygenation was worse than baseline. Conclusion: We conclude that the combination of iNO and i. v. PGI₂ might be more useful than either drug alone when severe pulmonary hypertension leading to impaired right ventricular function is present in ARDS. A systematic study of this observation is warranted. Received: 19 November 1998 Final revision received: 18 February 1999 Accepted: 12 April 1999     

The effects of prostacyclin on gastric intramucosal pH in patients with septic shock

Objective To investigate whether infusing prostacyclin (PGI₂) in patients with septic shock improves splanchnic oxygenation as assessed by gastric intramucosal pH (pHi).Design Interventional clinical study.Setting Surgical ICU in a university hospital.Patients 16 consecutive patients with septic shock according to the criteria of the ACCP/SCCM consensus conference all requiring norepinephrine to maintain arterial blood pressure.Interventions All patients received PGI₂ (10 ng/kg·min) after no further increase in oxygen delivery could be obtained by volume expansion, red cell transfusion and dobutamine infusion. The results were compared with those before and after conventional resuscitation. The patients received continuous PGI₂ infusion for 3–32 days.Measurements and results O₂ uptake was measured directly in the respiratory gases, pHi was determined by tonometry. Baseline O₂ delivery, O₂ uptake and pHi were 466±122 ml/min·m², 158±38 ml/min·m², and 7.29±0.09, respectively. While O₂ uptake remained unchanged, infusing PGI₂ increased O₂ delivery (from 610±140 to 682±155 ml/min·m²,p<0.01) and pHi (from 7.32±0.09 to 7.38±0.08,p<0.001) beyond the values obtained by conventional resuscitation. While 9 of 11 patients with final pHi>7.35 survived, all patients with final pHi<7.35 died (p<0.01).Conclusions Infusing PGI₂ in patients with septic shock increases pHi probably by enhancing blood flow to the splanchnic bed and thereby improves splanchnic oxygenation even when conventional resuscitation goals have been achieved.Presented in part at the 13th International Symposium on Intensive Care and Emergency Medicine, Brussels, March 1993     

Right ventricular function in COPD patients during weaning from mechanical ventilation

We studied the right ventricular function during a successful weaning period in 7 COPD patients without LV disease who had been mechanically ventilated for several days after an acute exacerbation of their disease. A Swan-Ganz ejection fraction thermodilution catheter performed measurements of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume index (RVEDVI) before and fifteen minutes after disconnection from the ventilator at the maintenance FiO₂. Although pulmonary artery pressure (PAP) rose from 25±4 to 28.5±4.5 mmHg after disconnection from the ventilator, RVEF (0.36±0.56 to 0.35±0.12) and RVEDVI (117±51 to 126±52 ml/m²) remained similar in both conditions. We concluded that right ventricular systolic function assessed with modified pulmonary artery catheter was maintained during the weaning phase in such weanable patients. This method could easily detect any fall of RVEF or diastolic RV enlargement able to impair the weaning in some patients.     

Influence of right ventricular pre‐ and afterload on right ventricular ejection fraction and preload recruitable stroke work relation

When right ventricular (RV) afterload is abnormally increased, it correlates inversely with right ventricular ejection fraction (RVEF). We tested, whether this would be different with normal afterload. Additionally, we investigated whether previous studies on the slope of RV preload recruitable stroke work (SW) relation, which used rather non‐physiological measures to change RV preload, could be transferred to more physiological loading conditions. RV volumes were determined by thermodilution in 16 patients with stable coronary artery disease and normal pulmonary artery pressure (PAP) at rest. Pre‐ and afterload were varied by body posture, nitroglycerin (NTG) application and by exercise at different body positions. At rest, the change from recumbent to sitting position decreased PAP, cardiac index (C_i), RV diastolic and systolic volumes, and RVEF. Additionally, mean pulmonary artery pressure (MPAP) correlated positively with both RVEF and cardiac index. After correction for mathematical coupling, the RV preload recruitable SW relation was: right ventricular stroke work index (RVSW_i) (10³ erg m^–2)= 8·1 × (RV end‐diastolic volume index ?4·9), with n=96, r=0·57, P≤0·001. Exercise abolished this correlation and led to an inverse correlation between RV end‐systolic volume (ESV) and RVSW. In conclusion, (i) RVEF correlates positively with RV afterload when afterload varies within normal range; (ii) the slope of the RV preload recruitable SW relation, which is obtained at steady state under normal loading conditions, is substantially flatter than previously described for dynamic changes of RV preload. With increasing afterload, preload loses its determining effect on RV performance, while afterload becomes more important. This puts earlier assumptions of an afterload independent RV preload recruitable SW relation into question.     

A comparison of dopamine,dobutamine and isoproterenol in the treatment of shock

Twelve patients in shock, defined as being present if the mean arterial blood pressure was less than 60 mm Hg, pulmonary arterial occlusion pressure was 15 mm Hg or greater, urine output was 20 ml or less for 2 consecutive hours, and there was clinical evidence of poor peripheral perfusion, underwent a comparative therapeutic trial with dopamine at 200 g · min^-1 and 400 g · min^-1 (2.5–5.5 g · kg^-1 · min^-1), dobutamine 250 g · min^-1 and 500 g · min^-1 (3.5–7 g · kg^-1 · min^-1) and isoproterenol 2 g · min^-1 and 4 g · min^-1 (0.025–0.055 g · kg^-1 · min^-1). Isoproterenol at 2 g · min^-1, produced a significant increase in pulse rate, cardiac output, left ventricular stroke work index and decrease in mean pulmonary blood pressure and pulmonary arterial occlusion pressure and at 4 g · min^-1 a significant increase in stroke volume, mixed venous oxygen tension and decrease in right atrial pressure and systemic vascular resistance was also observed. Dopamine at 200 g · min^-1 produced a significant increase in cardiac output, pulmonary arterial occlusion pressure and mixed venous oxygen tension and at 400 g · min^-1 a significant increase in pulse rate, mean arterial blood pressure mean pulmonary blood pressure, right ventricular stroke work index, right atrial pressure and pulmonary arterial occlusion pressure and decrease in arterial oxygen tension was also observed. Dobutamine at 250 g · min^-1 produced a significant increase in cardiac output, and at 500 g · min^-1 a significant increase in pulse rate, mixed venous oxgen tension and decrease in pulmonary arterial occlusion pressure.All agents increased pulse rate and cardiac output, although in the dosages chosen dopamine was the only agent do so with an increase in pulmonary arterial occlusion pressure and decrease in arterial oxygen tension. In patients in shock if an inotropic agent is considered necessary its pulmonary effect should be considered along with its effect on coronary and peripheral perfusion since dopamine may reduce arterial oxygenation.     

Pulmonary capillary pressure and gas exchange after E. coli bacteremia in pigs

In 9 Goettingen minipigs we studied the effect of E. coli bacteremia on effective pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance. Precapillary pressure gradient (dPa) was calculated as the difference between mean pulmonary artery pressure (MPP) and effective pulmonary capillary pressure (Pc) (dPa=MPP-Pc), postcapillary pressure gradient (dPv) as the difference between Pc and left atrial pressure (dPv=Pc-LAP). The disturbance of pulmonary gas exchange was quantified by the AaDO₂ quotient 1-PaO₂/PAO₂. Live E. coli infusion resulted in hypodynamic circulatory failure. Cardiac index fell from 3.7±0.8l·min^–1·m^–2 to 2.2±0.7l·min^–1·m^–2 after bacteremia lasting for 3.5 h. Simultaneously venous pulmonary vascular resistance rose from 25% of total pulmonary vascular resistance before to 32% after 3.5 h bacteremia, thus raising Pc from 11 mmHg to 16 mmHg. The degree of respiratory insufficiency was correlated with changes of MPP, dPa and dPv: 1-PaO₂/PAO₂=0.2+0.035·dPv (r=0.829). Our results show, that the longitudinal distribution of pulmonary vascular resistance changes during septicemia, thus raising Pc. This may be an important factor in the genesis of septic pulmonary failure.     

Angiocardiographic Pressure Volume Loops in the Analysis of Right Ventricular Function after Repair of Tetralogy of Fallot

Objective: The objective of the study was to estimate the capacity of pressure volume (PV) loop analysis to assess right ventricular (RV) function after Fallot (TOF) repair.Patients: Fifty six patients were examined after TOF repair. PV loops were constructed from RV angiocardiography and simultaneous pressure measurement. Patients were divided in three groups according to RV size and pressure (Group I: normal RV size and pressure; group II: enlarged RV, near normal pressure; group III: normal RV size, elevated pressure).Main outcome measures: Systolic stroke work corrected for body surface area (W/BSA) and for RV enddiastolic volume (W/EDV), peak RV filling (PFR) and emptying rates (PER) corrected for RV stroke volume, cycle efficiency (CE), RV ejection fraction (RVEF).Results: W/BSA was significantly higher in group II than in group I (0.19 ± 0.05 vs. 0.11 ± 0.04 J/m², p < 0.001) and was similar between groups II and III (0.19 ± 0.05 vs. 0.17 ± 0.05 J/m² ; NS). W/EDV was similar in groups I and II (12.4 ± 5.4 vs. 12.4 ± 2.9 mmHg; NS). CE was smallest in group II. The difference was significant between groups II and III (0.62 ± 0.08 vs. 0.73 ± 0.09; p < 0.05). RVEF was negatively correlated to RV end systolic volume (RVESV) in the patients of groups I and II (r = −0.32, p < 0.05). A similar correlation was found between PFR and RVESV (r = −0.28, p < 0.05).Conclusions: Analysis of a single PV loop allows quantification of RV load after TOF repair. W/BSA is increased to the same extent under volume and pressure load. The lack of decrease in W/EDV in patients with enlarged RV indicates that RV is capable to perform adequate work in a wide range. RVESV is a useful measure for estimating RV function after TOF repair depicting parameters of systolic and diastolic RV function.     

Non-invasive Evaluation of Right Ventricular Function with Real-Time 3-D Echocardiography

The aim of this study was to evaluate the accuracy and feasibility of real-time 3-D echocardiography (3-DE) in assessing right ventricular (RV) systolic function. A latex balloon was inserted into the right ventricle of 20 freshly harvested pig hearts which were then passively driven by a pulsatile pump apparatus. The RV global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS) and RV ejection fraction (RVEF), derived from 3-DE, as well as the RVEF obtained from 2-D echocardiography (2-DE) were quantified at different stroke volumes (30–70 mL) and compared with sonomicrometry data. In all comparisons, 3-D GLS, GCS, GAS, 2-D RVEF and 3-D RVEF exhibited strong correlations with sonomicrometry data (r = 0.89, 0.79, 0.74, 0.80, and 0.93, respectively; all p values < 0.001). Bland–Altman analyses revealed slight overestimations of echo-derived GLS, GCS, 2-DE RVEF and 3-DE RVEF compared with sonomicrometry values (bias = 1.55, 2.72, 3.59 and 2.21, respectively). Furthermore, there is better agreement among GLS, 3-D RVEF and the sonomicrometry values than between GCS and 2-D RVEF. Real-time 3-DE is more feasible and accurate for assessing RV function than 2-DE. GLS is a potential alternative parameter for quantifying RV systolic function.     

Right ventricular ejection fraction is better reflected by transverse rather than longitudinal wall motion in pulmonary hypertension

Background

Longitudinal wall motion of the right ventricle (RV), generally quantified as tricuspid annular systolic excursion (TAPSE), has been well studied in pulmonary hypertension (PH). In contrast, transverse wall motion has been examined less. Therefore, the aim of this study was to evaluate regional RV transverse wall motion in PH, and its relation to global RV pump function, quantified as RV ejection fraction (RVEF).

Methods

In 101 PH patients and 29 control subjects cardiovascular magnetic resonance was performed. From four-chamber cine imaging, RV transverse motion was quantified as the change of the septum-free-wall (SF) distance between end-diastole and end-systole at seven levels along an apex-to-base axis. For each level, regional absolute and fractional transverse distance change (SFD and fractional-SFD) were computed and related to RVEF. Longitudinal measures, including TAPSE and fractional tricuspid-annulus-apex distance change (fractional-TAAD) were evaluated for comparison.

Results

Transverse wall motion was significantly reduced at all levels compared to control subjects (p < 0.001). For all levels, fractional-SFD and SFD were related to RVEF, with the strongest relation at mid RV (R² = 0.70, p < 0.001 and R² = 0.62, p < 0.001). For TAPSE and fractional-TAAD, weaker relations with RVEF were found (R² = 0.21, p < 0.001 and R² = 0.27, p < 0.001).

Conclusions

Regional transverse wall movements provide important information of RV function in PH. Compared to longitudinal motion, transverse motion at mid RV reveals a significantly stronger relationship with RVEF and thereby might be a better predictor for RV function.     

Effects of rapid permissive hypercapnia on hemodynamics,gas exchange,and oxygen transport and consumption during mechanical ventilation for the acute respiratory distress syndrome

Objective To measure the effects of rapid permissive hypercapnia on hemodynamics and gas exchange in patients with acute respiratory distress syndrome (ARDS).Design Prospective study.Setting: 18-bed, medical intensive care unit, university hospital.Patients 11 mechanically ventilated ARDS patients.Intervention Patients were sedated and ventilated in the controlled mode. Hypercapnia was induced over a 30–60 min period by decreasing tidal volume until pH decreased to 7.2 and/or P₅₀ increased by 7.5 mmHg. Settings were then maintained for 2 h.Results Minute ventilation was reduced from 13.5±6.1 to 8.2±4.1l/min (mean±SD), PaCO₂ increased (40.3±6.6 to 59.3±7.2 mmHg), pH decreased (7.40±0.05 to 7.26±0.05), and P₅₀ increased (26.3±2.02 to 31.1±2.2 mmHg) (p<0.05). Systemic vascular resistance decreased (865±454 to 648±265 dyne·s·cm^–5, and cardiac index (CI) increased (4±2.4 to 4.7±2.4 l/min/m²) (p<0.05). Mean systemic arterial pressure was unchanged. Pulmonary vascular resistance was unmodified, and mean pulmonary artery pressure (MPAP) increased (29±5 to 32±6 mmHg,p<0.05). PaO₂ remained unchanged, while saturation decreased (93±3 to 90±3%,p<0.05), requiring an increase in FIO₂ from 0.56 to 0.64 in order to maintain an SaO₂>90%. PvO₂ increased (36.5±5.7 to 43.2±6.1 mmHg,p<0.05), while saturation was unmodified. The arteriovenous O₂ content difference was unaltered. Oxygen transport (DO₂) increased (545±240 to 621±274 ml/min/m²,p<0.05), while the O₂ consumption and extraction ratio did not change significantly. Venous admixture (Q_va/Q_t) increased (26.3±12.3 to 32.8±13.2,p<0.05).Conclusions These data indicate that acute hypercapnia increases DO₂ and O₂ off-loading capacity in ARDS patients with normal plasma lactate, without increasing O₂ extraction. Whether this would be beneficial in patients with elevated lactate levels, indicating tissue hypoxia, remains to be determined. Furthermore, even though hypercapnia was well tolerated, the increase in Q_va/Q_t, CI, and MPAP should prompt caution in patients with severe hypoxemia, as well as in those with depressed cardiac function and/or severe pulmonary hypertension.     

Correlation of right ventricular ejection fraction and tricuspid annular plane systolic excursion in tetralogy of Fallot by magnetic resonance imaging

The correlation between right ventricular ejection fraction (RVEF) and tricuspid annular plane systolic excursion (TAPSE) by two-dimensional (2-D) echo has been repeatedly validated, but not by magnetic resonance imaging (MRI) nor in patients with congenital heart disease. We tested whether TAPSE measurements by MRI correlate with RVEF in surgically repaired tetralogy of Fallot (TOF) patients. TAPSE was measured from systolic displacement of the RV-freewall/tricuspid annular plane junction in the apical 4-chamber view in 7 normal subjects and 14 TOF patients. The RV was reconstructed in 3-D from manually traced borders on MR images to compute true EF. Because we previously observed discrepancy between TAPSE and RVEF in the presence of regional dysfunction, we also analyzed RV wall motion in terms of regional stroke volume at 20 short axis slices from apex to tricuspid annulus. RVEF was 52 ± 3% in normal subjects and 41 ± 9% in TOF (P < 0.01). TAPSE correlated weakly (r = 0.50, P < 0.05) with RVEF. TOF patients exhibited increased regional stroke volume from apical portions of the RV and decreased regional stroke volume at the base compared to normal (P < 0.05 at 15 of 20 slices). Regional stroke volume in apical slices correlated inversely with RVEF such that patients with higher apical stroke volume had lower RVEF (P < 0.05). TAPSE is not a reliable measure of RVEF in TOF by MRI. TAPSE may be of limited use in conditions that exhibit abnormal regional contraction.     

Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla

Background

Functional and morphologic assessment of the right ventricle (RV) is of clinical importance. Cardiovascular magnetic resonance (CMR) at 1.5T has become gold standard for RV chamber quantification and assessment of even small wall motion abnormalities, but tissue analysis is still hampered by limited spatial resolution. CMR at 7T promises increased resolution, but is technically challenging. We examined the feasibility of cine imaging at 7T to assess the RV.

Methods

Nine healthy volunteers underwent CMR at 7T using a 16-element TX/RX coil and acoustic cardiac gating. 1.5T served as gold standard. At 1.5T, steady-state free-precession (SSFP) cine imaging with voxel size (1.2x1.2x6) mm³ was used; at 7T, fast gradient echo (FGRE) with voxel size (1.2x1.2x6) mm³ and (1.3x1.3x4) mm³ were applied. RV dimensions (RVEDV, RVESV), RV mass (RVM) and RV function (RVEF) were quantified in transverse slices. Overall image quality, image contrast and image homogeneity were assessed in transverse and sagittal views.

Results

All scans provided diagnostic image quality. Overall image quality and image contrast of transverse RV views were rated equally for SSFP at 1.5T and FGRE at 7T with voxel size (1.3x1.3x4)mm³. FGRE at 7T provided significantly lower image homogeneity compared to SSFP at 1.5T. RVEDV, RVESV, RVEF and RVM did not differ significantly and agreed close between SSFP at 1.5T and FGRE at 7T (p=0.5850; p=0.5462; p=0.2789; p=0.0743). FGRE at 7T with voxel size (1.3x1.3x4) mm³ tended to overestimate RV volumes compared to SSFP at 1.5T (mean difference of RVEDV 8.2±9.3ml) and to FGRE at 7T with voxel size (1.2x1.2x6) mm³ (mean difference of RVEDV 9.3±8.6ml).

Conclusions

FGRE cine imaging of the RV at 7T was feasible and provided good image quality. RV dimensions and function were comparable to SSFP at 1.5T as gold standard.     

Influence of nimodipine and nifedipine on intrapulmonary shunting — a comparison to other vasoactive drugs

This study was assigned to investigate the influence of calcium channel blockers (nimodipine and nifedipine) in comparison to other vasoactive drugs (nitroglycerin, dopamine) on pulmonary shunting (Qs/Qt). Fifty anesthetised patients scheduled for aortocoronary bypass operation were randomly allocated to 5 groups receiving one of the following drugs: (1) nimodipine 1.0 g·kg^-1·min^-1; (2) nifedipine 0.7 g·kg^-1·min^-1; (3) nitroglycerin (TNG) 0.5 g ·kg^-1·min^-1; (4) dopamine; (5) g·kg^-1·min^-1; (6) placebo (0.9% NaCl). Nimodipine as well as nifedipine led to a significant increase in cardiac output (+44%; +39%), pulmonary vascular resistance simultaneously decreased (-25%;-28%). PaO₂ increased significantly (+16%; +13%), too, whereas Qs/Qt remained almost unchanged. In contrast, the increase in cardiac output induced by dopamine (+27%) was accompanied by a significant increase in shunting (+34%). TNG application did not alter Qs/Qt, but pulmonary artery pressure (PAP) decreased markedly (-19%).