Inaccuracy of pulmonary capillary wedge pressure when compared to left atrial pressure in the early postsurgical period

Impact of Interventricular Interaction on Ventricular Function: Insights From Right Ventricular Pressure-Volume Analysis

BACKGROUND

Interventricular interactions may be responsible for the decline in ventricular performance observed in various disease states that primarily affect the contralateral ventricle.

OBJECTIVES

This study sought to quantify the impact of such interactions on right ventricular (RV) size and function using clinically stable individuals with left ventricular assist devices (LVADs) as a model for assessing RV hemodynamics while LV loading conditions were acutely manipulated by changing device speed during hemodynamic optimization studies (ie, ramp tests).

METHODS

The investigators recorded RV pressure-volume loops with a conductance catheter at various speeds during ramp tests in 20 clinically stable HeartMate3 recipients.

RESULTS

With faster LVAD speeds and greater LV unloading, indexed RV end-diastolic volume increased (72.28 ± 15.07 mL at low speed vs 75.95 ± 16.90 at high speed; P = 0.04) whereas indexed end-systolic volumes remained neutral. This resulted in larger RV stroke volumes and shallower end-diastolic pressure-volume relationships. Concurrently, RV end-systolic pressure decreased (31.58 ± 9.75 mL at low speed vs 29.58 ± 9.41 mL at high speed; P = 0.02), but contractility, as measured by end-systolic elastance, did not change significantly. The reduction in RV end-systolic pressure was associated with a reduction in effective arterial elastance from 0.65 ± 0.43 mm Hg/mL at low speed to 0.54 ± 0.33 mm Hg/mL at high speed (P = 0.02).

CONCLUSIONS

Interventricular interactions resulted in improved RV compliance, diminished afterload, and did not reduce RV contractility. These data challenge the prevailing view that interventricular interactions compromise RV function, which has important implications for the understanding of RV-LV interactions in various disease states, including post-LVAD RV dysfunction.

Tissue Doppler Imaging (E/e') and Pulmonary Capillary Wedge Pressure in Patients With Severe Aortic Stenosis

OBJECTIVE

Although American and European consensus statements advocate using the ratio of the transmitral E velocity and tissue Doppler early diastolic mitral annular velocity (E/e') in the assessment of left-sided heart filling pressures, recent reports have questioned the reliability of this ratio to predict left atrial pressures in a variety of disease states. The authors hypothesized that there is a clinically significant correlation between E/e' and pulmonary capillary wedge pressure (PCWP) in patients with severe aortic stenosis.

DESIGN

Retrospective cohort study.

PARTICIPANTS

The study comprised 733 consecutive patients with severe aortic stenosis who underwent transcatheter aortic valve replacement for severe aortic stenosis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

PCWP and E/e'_ave (average of the lateral and medial annulus tissue Doppler velocities) were measured with a pulmonary artery catheter and transthoracic echocardiography during preprocedural evaluation. Patients were grouped by left ventricular ejection fraction (LVEF) ≥50% and LVEF <50%. Spearman rank correlation, analysis of variance, and t and chi-square tests were used to analyze the data. Seventy-nine patients met the inclusion criteria. There was no significant correlation between E/e'_ave and PCWP (n = 79, Spearman r = 0.096; p = 0.3994). This correlation did not improve when ventricular function was considered (LVEF <50%: n = 11, Spearman r = -0.097; p = 0.776 and LVEF ≥50%: n = 68, Spearman r = 0.116; p = 0.345). There was no statistically significant difference in mean PCWP between each range of E/e'_ave.

CONCLUSION

A clinically relevant relationship between E/e' and PCWP was not observed in patients with severe aortic stenosis.

Wedging the Pulmonary Artery Catheter: Changes in Left Atrial and Pulmonary Artery Pressures and Risk for Perforation

OBJECTIVE

Clinical and experimental data indicate that when there is lung disease, wedging the pulmonary artery catheter (PAC) could cause decreases in cardiac output and systemic arterial blood pressure and an increase in mean pulmonary artery pressure (PAP). The authors studied whether wedging would alter mean left atrial pressure (LAP), and report perforations with PACs in their unit since 1975.

DESIGN

Observational study.

SETTING

University hospital operating room and intensive care unit.

PARTICIPANTS

Ten adult patients undergoing cardiac surgery.

INTERVENTIONS

Placement of epidural catheters in the left atrium and pulmonary artery, and a PAC.

MEASUREMENTS AND MAIN RESULTS

After weaning from cardiopulmonary bypass, mean LAP, mean PAP, and cardiac output were measured before and during wedging with the chest open and closed. Mean LAP decreased during wedging, from 13.5 +/- 2.8 (SD) mmHg to 13.0 +/- 3.0 mmHg (open chest) and from 15.8 +/- 3.2 mmHg to 15.3 +/- 3.1 mmHg (closed chest; p < 0.001), and mean PAP increased, from 18.8 +/- 3.5 mmHg to 19.7 +/- 3.5 mmHg (open chest) and from 21.3 +/- 4.3 mmHg to 21.9 +/- 4.2 mmHg (closed chest; p < 0.001). Mean PAP-mean LAP increased by 20% to 25%. Wedge pressure did not differ from mean LAP. Cardiac output and systemic arterial pressure did not change. Four perforations due to PACs occurred since 1975.

CONCLUSIONS

In adult patients undergoing cardiac surgery, wedging of a PAC resulted in a small decrease in mean LAP and a small increase in mean PAP. The wedging maneuver carries a small risk. How wedging is performed could influence the risk for perforation.

Pulmonary artery occlusion pressure and central venous pressure fail to predict ventricular filling volume, cardiac performance, or the response to volume infusion in normal subjects

OBJECTIVE

Pulmonary artery occlusion pressure and central venous pressure have been considered to be reliable measures of left and right ventricular preload in patients requiring invasive hemodynamic monitoring. Studies in recent years have questioned the correlation between these estimates of ventricular filling pressures and ventricular end-diastolic volumes/cardiac performance variables in specific patient groups, but clinicians have continued to consider the relationship valid in the broader context. The objective of this study was to assess the relationship between pressure estimates of ventricular preload (pulmonary artery occlusion pressure, central venous pressure) and end-diastolic ventricular volumes/cardiac performance in healthy volunteers.

DESIGN

Prospective, nonrandomized, nonblinded interventional study.

SETTING

Cardiac catheterization and echocardiography laboratories.

SUBJECTS

Normal healthy volunteers (n = 12 group 1, n = 32 group 2).

INTERVENTIONS

Pulmonary catheterization and radionuclide cineangiography (group 1) and volumetric echocardiography (group 2) during 3 L of normal saline infusion over 3 hrs.

MEASUREMENTS AND MAIN RESULTS

In group 1, the initial pulmonary artery occlusion pressure and central venous pressure did not correlate significantly with initial end-diastolic ventricular volume indexes or cardiac performance (cardiac index and stroke volume index). Changes in pulmonary artery occlusion pressure and central venous pressure following saline infusion also did not correlate with changes in end-diastolic ventricular volume indexes or cardiac performance. In contrast, initial end-diastolic ventricular volume indexes and changes in these ventricular volume indexes in response to 3 L of normal saline loading correlated well with initial stroke volume index and changes in stroke volume index, respectively. The relationship between left ventricular end-diastolic volume index and stroke volume index was confirmed in group 2 subjects using mathematically independent techniques to measure these variables. In addition, initial central venous pressure, right ventricular end-diastolic volume index, pulmonary artery occlusion pressure, and left ventricular end-diastolic volume index failed to correlate significantly with changes in cardiac performance in response to saline infusion in group 1 subjects.

CONCLUSIONS

Normal healthy volunteers demonstrate a lack of correlation between initial central venous pressure/pulmonary artery occlusion pressure and both end-diastolic ventricular volume indexes and stroke volume index. Similar results are found with respect to changes in these variables following volume infusion. In contrast, initial end-diastolic ventricular volume indexes and changes in end-diastolic ventricular volume indexes in response to saline loading correlate strongly with initial and postsaline loading changes in cardiac performance as measured by stroke volume index. These data suggest that the lack of correlation of these variables in specific patient groups described in other studies represents a more universal phenomenon that includes normal subjects. Neither central venous pressure nor pulmonary artery occlusion pressure appears to be a useful predictor of ventricular preload with respect to optimizing cardiac performance.

Pulmonary venous pressure: relationship to pulmonary artery, pulmonary wedge, and left atrial pressure in normal, lightly sedated dogs

Because pulmonary venous pressure has never been measured, it is unclear whether pulmonary wedge pressure measures left atrial pressure, as commonly assumed, or pressure more upstream in the pulmonary venous or capillary beds. Fluid-filled mean pulmonary artery and pulmonary wedge pressure were compared with pulmonary venous and left atrial pressure obtained with high-fidelity micromanometer catheters in eight lightly sedated dogs over a physiologic range of filling pressures. In all conditions, mean pulmonary wedge pressure was virtually identical (r = 0.99) to mean left atrial pressure (slope = 0.99; intercept = -0.46 mm Hg). At the same time, mean pulmonary venous pressure (17.1 +/- 6.5 mm Hg) was intermediate between mean pulmonary artery pressure (20.2 +/- 6.2 mm Hg) and mean pulmonary wedge pressure (13.3 +/- 6.2 mm Hg; P < 0.0001) or mean left atrial pressure (13.4 +/- 6.3 mm Hg; P < 0.0001). These relationships were maintained over normal and increased pressure ranges. As measured by conventional flow-directed pulmonary catheters, mean pulmonary wedge pressure accurately reflects left atrial pressure in lightly sedated, spontaneously breathing normal dogs.

Biphasic changes in left ventricular function during hyperdynamic endotoxemia

Cardiac contractility was studied in a clinically relevant conscious swine model simulating human hemodynamics during endotoxemia. The slope of the end-systolic pressure-volume relationship [end-systolic elastance (EES)] was used as a load-independent contractility index. Chronic instrumentation in 10 pigs included two pairs of endocardial ultrasonic crystals for measuring internal major and minor axial dimensions of the left ventricle, a micromanometer for left ventricular pressure measurement, and a thermodilution pulmonary artery catheter. After a 10-day recovery period, control measurements of cardiac hemodynamic function were obtained. The following week, Escherichia coli endotoxin (10 micrograms . kg-1. h-1) was administered intravenously for 24 h. EES increased 1 h after endotoxin infusion and decreased beyond 7 h. The later hemodynamic changes resembled human cardiovascular performance during endotoxemia more closely than the changes during the acute phase. EES decreased in the later phase. A similar biphasic response of EES has been reported during a tumor necrosis factor-alpha (TNF) challenge. Even though plasma TNF was highest at 1 h and declined thereafter in this study, no consistent relationship between TNF and EES was identified, and TNF levels did not correlate directly with the changes in EES.

Determinants of myocardial performance after blunt chest trauma

OBJECTIVE

This study investigates whether factors that determine myocardial performance (preload, afterload, heart rate, and contractility) are altered after isolated unilateral pulmonary contusion.

METHODS

Catheters were placed in the carotid arteries, left ventricles, and pulmonary arteries of anesthetized, ventilated (FiO2=0.5) pigs (31.2+/-0.6 kg; n=26). A unilateral, blunt injury to the right chest was delivered with a captive bolt gun (n=17) followed by tube thoracostomy. To control for anesthesia and instrumentation at FiO2 of 0.5, one group received tube thoracostomy only (sham injury; n=6). To control for effects of hypoxia without chest injury, an additional sham-injury group (n=3) was ventilated with FiO2 of 0.12. To generate cardiac function (i.e., Starling) curves, lactated Ringer's solution was administered in three bolus infusions at serial time points; the slope of stroke index versus ventricular filling pressure defines cardiac contractility.

RESULTS

By 4 hours after pulmonary contusion, pulmonary vascular resistance, airway resistance, and dead space ventilation were increased, whereas PaO2 (72+/-6 mm Hg at FiO2=0.5) and dynamic compliance were decreased (all p < 0.05). Despite profound lung injury, arterial blood pressure, heart rate, cardiac filling pressures, and output remained within the normal range, which is inconsistent with direct myocardial contusion. The slope of pulmonary capillary wedge pressure versus left ventricular end-diastolic pressure (LVEDP) regression was reduced by more than 50% from baseline (p < 0.05), but there was no significant change in the slope of the central venous pressure versus LVEDP regression. By 4 hours after contusion, the slope of the stroke index versus LVEDP curve was reduced by more than 80% from baseline (p < 0.05). By the same time after sham injury with FiO2 of 0.12 (PaO2 < 50 mm Hg), the regression had decayed a similar amount, but there was no change in the slope after sham injury with FiO2 of 0.5 (PaO2 > 200 mm Hg).

CONCLUSION

After right-side pulmonary contusion, the most often used estimate of cardiac preload (pulmonary capillary wedge pressure) does not accurately estimate LVEDP, probably because of changes in the pulmonary circulation or mechanics. Central venous pressure is a better estimate of filling pressure, at least in these conditions, probably because it is not directly influenced by the pulmonary dysfunction. Also, ventricular performance can be impaired by depressed myocardial contractility and increased right ventricular afterload even with normal left ventricular afterload and preload. It is thus conceivable that occult myocardial dysfunction after pulmonary contusion could have a role in the progression to cardiorespiratory failure even without direct cardiac contusion.

Starling resistor effects on pulmonary artery occlusion pressure in endotoxin shock provide inaccuracies in left ventricular compliance assessments

OBJECTIVES

Assessment of left ventricular preload and left ventricular compliance changes in septic shock using pulmonary artery occlusion pressure (PAOP) presumes that this pressure accurately reflects left heart filling pressure. We tested the hypothesis that Starling resistor forces render PAOP inaccurate as an index of left heart filling pressure, resulting in misleading assessments of left ventricular compliance changes.

DESIGN

Prospective, randomized, controlled study.

SETTING

Large-animal research laboratory at a university.

SUBJECTS

Fourteen anesthetized domestic pigs weighing 20 to 25 kg.

INTERVENTIONS

Pulmonary artery flotation catheters and systemic arterial catheters were placed via right cervical vessels. The left atrium was directly catheterized for left atrial pressure measurements. Left ventricular end-diastolic diameter was measured using sonomicrometry. Other measured or calculated variables were mean arterial pressure, mean pulmonary arterial pressure, PAOP, pulmonary capillary pressure, and pulmonary arterial and venous resistances. Pigs received endotoxin (0.5 mg/kg i.v. over 30 mins), or an equivalent volume of saline. At t = 60 mins, pigs were resuscitated with lactated Ringer's solution (40 mL/kg over 30 mins). Measurements were taken before and after endotoxin administration, and immediately and 30 mins after lactated Ringer's solution administration. Data were analyzed by two-way analysis of variance (p < or = .05).

MEASUREMENTS AND MAIN RESULTS

PAOP, mean pulmonary arterial pressure, and pulmonary capillary pressure increased after endotoxin infusion, while left atrial pressure and left ventricular end-diastolic diameter decreased. Left atrial pressure and left ventricular end-diastolic diameter returned to baseline immediately after lactated Ringer's solution administration, while PAOP remained increased. Pulmonary arterial resistance and pulmonary venous resistance increased after endotoxin administration, with pulmonary venous resistance showing the greater percent increase. Pulmonary venous resistance decreased transiently immediately after lactated Ringer's solution administration. These changes were not observed in the control group. Accordingly, comparisons of PAOP vs. left ventricular end-diastolic diameter, and left atrial pressure vs. left ventricular end-diastolic diameter yielded divergent results.

CONCLUSIONS

The dissociation between PAOP and left atrial pressure, while left ventricular and -diastolic diameter (preload volume) decreased, and changes in pulmonary venous resistance, are strong evidence for Starling resistor forces (venocompression) rather than active venoconstriction. These data indicate that PAOP overestimates left atrial pressure during endotoxin shock, making it an inaccurate index of left ventricular preload. This overestimation can cause misleading assessments of left ventricular compliance.

Systemic gaseous microemboli during left atrial catheterization: a common occurrence?

OBJECTIVE

Gaseous microemboli during cardiac surgery have been implicated as a potential cause of postoperative neurologic injury. Any monitoring technique that exposes the systemic circulation to atmospheric pressure could introduce gaseous microemboli, causing cerebral microembolization. The incidence of carotid artery gaseous microemboli was studied during left atrial catheter insertion.

DESIGN

Prospective clinical study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Twelve patients undergoing elective cardiac surgery.

INTERVENTIONS

Perioperatively, a 5-MHz continuous wave Doppler probe was positioned over the left carotid artery to maximally record blood flow signals. The criteria used for detecting a gaseous microembolus were a sudden increase in the amplitude of the visual signal by 30% and a characteristic audible sound.

MEASUREMENTS AND MAIN RESULTS

Numbers of microemboli at three timepoints (before and during left atrial catheter insertion and during catheter flushing) were assessed using the Friedman test. No emboli were detected before left atrial catheter insertion. When compared with the preinsertion time period, statistically (p < 0.05) significant numbers of gaseous microemboli were found in six patients during catheter insertion (3 +/- 1 microemboli; range 1 to 7 microemboli) and in five patients during catheter flushing (5 +/- 2 microemboli; range 1 to 12 microemboli). There was a tendency for patients with lower filling pressures to entrain more microemboli during insertion (r = 0.44; p = 0.149). No patient showed evidence of gross neurologic dysfunction postoperatively, although sensitive neurologic testing was not performed.

CONCLUSIONS

Left atrial catheter insertion and flushing can cause systemic gaseous microemboli in more than 50% of patients. Although the number of microemboli introduced is relatively small, extreme care should be used during left atrial catheter insertion.

Accurate measurement of the transmitral gradient in patients with mitral stenosis: a simultaneous catheterization and Doppler echocardiographic study

OBJECTIVES

This study compared the accuracy of Doppler echocardiography with that of conventional cardiac catheterization in the measurement of transmitral gradients in patients with mitral stenosis.

BACKGROUND

Simultaneous measurement of left atrial and left ventricular pressures is the most accurate method for determination of the mean mitral valve gradient in patients with mitral stenosis. Because of the inherent risks of transseptal catheterization, pulmonary capillary wedge pressure has been used in many invasive laboratories for determination of the mean mitral valve gradient. Recent studies have observed significant errors when pulmonary capillary wedge pressure was used for these measurements. Doppler echocardiography provides a noninvasive alternative for measurement of the transmitral gradient, but its relative accuracy has remained unclear.

METHODS

Seventeen patients with mitral stenosis who underwent transseptal cardiac catheterization had simultaneous measurement of 1) transmitral gradient by direct left atrial and left ventricular pressures, 2) transmitral gradient by pulmonary capillary wedge and left ventricular pressures, and 3) transmitral gradient by Doppler echocardiography.

RESULTS

Transmitral gradient measured by pulmonary capillary wedge and left ventricular pressures significantly overestimated the gradient obtained by direct measurement of left atrial pressure, with a mean (+/- SD) difference of 3.3 +/- 3.5 mm Hg (or 53%). Correcting the pulmonary capillary wedge pressure for the phase shift resulted in better correlation, but a consistent overestimation still remained, with a mean difference of 2.5 +/- 2.9 mm Hg (or 43%). The best correlation with the smallest variability was comparison of the Doppler-derived mean gradient with the gradient from direct measurement of left atrial and left ventricular pressures, with a mean difference of 0.2 +/- 1.2 mm Hg.

CONCLUSIONS

Compared with the transmitral gradient obtained by direct measurement of left atrial and left ventricular pressures, the Doppler-derived gradient is more accurate than that obtained by conventional cardiac catheterization and should be considered the reference standard.

Hemodynamic effects of lobar pulmonary artery occlusion in a porcine sepsis model

We induced severe pulmonary hypertension and acute lung injury in 6 pigs by Pseudomonas aeruginosa infusion. We studied the effect of pulmonary artery catheter inflation of a pulmonary artery catheter balloon in the left lower lobar pulmonary artery was accompanied by a significant (p less than 0.05, paired t test) increase in pulmonary artery pressure, a decrease in left atrial pressure, a decrease in cardiac output, and a decrease in mean arterial pressure. No significant changes occurred when the catheter was advanced into the wedged position without balloon inflation. Balloon inflation had no significant effect on these variables before bacterial infusion. We conclude that with sufficiently severe pulmonary hypertension in association with diffuse lung injury, lobar pulmonary artery occlusion may cause alterations in cardiac output and left atrial pressure. This may confuse interpretation of pulmonary artery catheter measurements.

Pulmonary artery occlusion pressure is not accurate immediately after cardiopulmonary bypass

Elevated pulmonary vascular resistance (PVR), differential cardiac dynamics, and increased lung water following cardiopulmonary bypass (CPB) have been proposed as limitations to the accuracy of the pulmonary artery occlusion pressure (PAOP) in estimating left ventricular preload. A prospective study of 22 patients undergoing elective myocardial revascularization is described wherein PAOP was compared with directly measured left atrial pressure (LAP). The reliability of PAOP to estimate LAP in the hour immediately following CPB and at 1, 4, 8, and 12 hours post-CPB was examined with repeated measures analysis of variance. Relationships between the PAOP-LAP difference and PVR, core temperature, arterial CO2 tension, and right and left ventricular stroke work indices (RVSWI, LVSWI) were tested by linear regression analysis. There was greater variability in measurements at 15, 30, and 45 minutes immediately after CPB, demonstrated by a pooled correlation coefficient of 0.73 versus 0.90 in the postoperative period. The degree of discrepancy between PAOP and LAP lessened with time. There was no determinable relationship of the PAOP-LAP gradient to PVR, level of PCO2, temperature, RVSWI, or LVSWI. Potential sources of discrepancy include airway pressure effects, position of the measuring catheters, positive end-expiratory pressure, infusion of protamine sulfate, extremes of pulmonary artery pressures, and effects of an open pericardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative echocardiography in mitral and tricuspid valve repair

Echocardiography with Doppler color flow mapping is a very useful intraoperative technique in patients undergoing mitral or tricuspid valve repair. In the patient who is a repair candidate, this technique can be used intraoperatively to answer important clinical questions: the severity of the regurgitation; the morphological basis of the regurgitant lesion; and the feasibility of repair. Other important issues such as the impact of physiological interventions on regurgitation severity, the presence of associated lesions, and the state of ventricular function can also be addressed. In the patient who has undergone a valve repair, this technique can be used intraoperatively prior to chest closure to assess the adequacy of the repair procedure and to detect associated complications such as outflow tract obstruction.

Left ventricular function in the early postoperative stage--cardioplegic baneful effect is lost in the first 24 hours

Early postoperative left ventricular function was investigated in 42 patients with left ventricular volume overload caused by valvular regurgitation. Preoperatively, left ventricular contractile function, stroke work and stress relations were all evaluated. Anoxic index (AnI) was considered as an index of myocardial preservation. Postoperatively, the cardiac function was estimated as the left ventricular stroke work index (SWI) after 3, 6, 24 and 48 hours of post-cardiopulmonary bypass. The release of CK-MB isoenzyme was also measured at the same time as an indication of myocardial injury. AnI and the postoperative SWI3 and SWI6 showed negative correlations in 6 hours, while preoperative SWI0 and postoperative SWI24 and SWI48 showed positive correlations after 24 hours, and SWI0 showed positive or negative correlations to the preoperative 8 parameters. It was observed that ejection fraction, end-systolic wall stress to end-systolic volume index ratio and tension volume ejection showed positive, while left ventricular end-diastolic pressure showed negative correlations to SWI48. However, none of these indexes showed any significant correlations during the first 24 hours following surgery. On the other hand, AnI and the total release of CK-MB isoenzyme showed a positive correlation. These data suggest that the cardioplegic baneful effect on cardiac function might be lost in the first 24 hours after surgery.

Effect of nitroglycerin during hemodynamic estimation of valve orifice in patients with mitral stenosis

In patients with mitral stenosis, valve orifice calculations using pulmonary capillary wedge pressure as a substitute for left atrial pressure may overestimate the severity of disease. Previous studies have shown that mitral valve area determined from transseptal left atrial pressure measurements exceeds that area derived from pulmonary wedge pressure measurements. This is probably due to pulmonary venoconstriction, which is reversed by nitroglycerin. Nitroglycerin, 0.4 mg, was administered sublingually to 20 patients with mitral valve disease during preoperative cardiac catheterization using the pulmonary capillary wedge pressure as the proximal hydraulic variable. At the time of a peak hypotensive effect, 3 to 5 minutes after nitroglycerin administration, the mean pulmonary capillary wedge pressure decreased from 23 +/- 2 (mean +/- SEM) to 19 +/- 2 mm Hg (p less than 0.005). The mean diastolic transmitral pressure gradient (12.6 +/- 1.2 mm Hg before and 11.5 +/- 1.0 mm Hg after nitroglycerin; p = NS) and cardiac output (4.0 +/- 0.3 to 4.1 +/- 0.3 liters/min; p = NS) did not change significantly. Nevertheless, the hemodynamic mitral orifice area, calculated using the Gorlin formula, increased from 0.8 +/- 0.1 to 1.1 +/- 0.2 cm2 (p less than 0.05). In 12 patients with isolated mitral stenosis, without regurgitation, the mitral valve orifice area after nitroglycerin was 0.4 +/- 0.2 cm2 larger than it was before drug administration (p less than 0.05). Administration of nitroglycerin during evaluation of mitral stenosis eliminates pulmonary venoconstriction, which raises the pulmonary capillary wedge pressure above the left atrial pressure in some patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Unreliability of hemodynamic indexes of left ventricular size during cardiac surgery

Pulmonary artery diastolic (PADP) and wedge pressures (PAWP) and left ventricular end-diastolic pressure (LVEDP) are commonly used to estimate left ventricular (LV) preload. To assess the ability of hemodynamic indexes of preload to estimate anatomical preload, or LV volume, we studied 45 patients during a coronary (18 patients) or aortic valve (27 patients) procedure and compared epicardial two-dimensional echocardiographic LV cavity area with simultaneous measurements of PADP, PAWP, and high-fidelity LVEDP. Pulmonary artery diastolic pressure, PAWP, and their percent change after bypass did not correlate with absolute values (before or after bypass) or percent change in LVEDP. Percent change in LV area correlated weakly with percent change in PADP (r = .34, p less than .03) but not with changes in PAWP or LVEDP. Changes were opposite in direction in 45% (PADP), 50% (PAWP), and 67% (LVEDP) of patients. In conclusion, both PADP and PAWP were poor guides to LVEDP and neither reflected changes in LV size. Thus, hemodynamic indexes of preload should be used with caution during cardiac operations.

Left atrial and ventricular transseptal catheterization review: losing skills?

Transseptal catheterization has been routinely done at this institution for the past 19 years to evaluate the left heart. Reviewing the last 250 consecutive transseptal heart catheterizations between 1978 and 1986, the left atrium and ventricle were entered in all but six patients. One death occurred with four other major complications. There were 177 males and 73 females ranging from 18 to 84 years of age. Of these 250 studies, 31 were in association with direct left ventricular apical puncture; 42 were in patients with subaortic stenosis; 101 were in aortic stenosis; 26 were in patients with combined aortic and mitral disease; and four were in patients with triple prosthetic valve replacements. No attempts were made to cross the prosthetic mitral valves. A decline in the number of transseptal studies at this institution has been noted over the past 8 years and the technique is not longer taught routinely to Fellows. The reduction is due to increased emphasis on coronary artery anatomy, fewer rheumatic and prosthetic valvular admissions, and improved reevaluation by non-invasive echocardiography and doppler studies. This has resulted in a loss in proficiency among invasive cardiologists. In conclusion, the transseptal technique is potentially hazardous, but continued usage will maintain proficiency and a low major and minor complication rate.

Echocardiographic estimate of left atrial pressure in children

Echocardiographic estimates of left atrial pressure using the Q-MVC/AVC-E ratio were obtained from 21 patients in the early postoperative period and compared to simultaneously recorded mean left atrial pressure. A good correlation was obtained between mean left atrial pressure and the Q-MVC/AVC-E ratio (r = 0.81, p less than 0.001) with a regression equation of: left atrial pressure = 11.09 (Q-MVC/AVC-E) + 0.84. The present data compared to those of previous investigators reveal that, although there are quantitative differences between each of the studies, the correlation coefficient of each study is good. Echocardiography provides a useful noninvasive estimate the left atrial pressure; however, each laboratory must establish its own normals.

Misleading "pulmonary wedge pressure" after pneumonectomy: its importance in postoperative fluid therapy

Patients who have undergone pneumonectomy are reported to be at increased risk of serious pulmonary edema. Monitoring fluid therapy using the Swan-Ganz balloon-tipped catheter is therefore important in the perioperative management of these patients. Pulmonary artery occlusion pressure (PAOP), determined by inflating a balloon to occlude a branch of the pulmonary artery, is routinely used to measure pulmonary wedge pressure (PWP). In turn, PWP reflects left atrial pressure (LAP). We clinically observed postpneumonectomy patients in whom pulmonary edema developed, but whose PAOP was near normal. Our findings led us to suspect that PAOP in such patients may reflect a falsely low PWP value. We hypothesized that after pneumonectomy inflation of the balloon on the Swan-Ganz catheter to obtain PWP can result in considerable occlusion of the remaining cross-sectional area of pulmonary circulation. This occlusion acutely increases the right ventricular afterload, resulting in reduced cardiac output and reduced LAP. Although the PAOP under these circumstances still accurately reflects the LAP, these values have been artificially lowered; hence, they result in falsely low PWP readings. To verify this hypothesis, the following canine experiments were performed. Five dogs were monitored with a Swan-Ganz catheter, a left atrial catheter, and an electromagnetic flow probe applied to a carotid artery. Before pneumonectomy, inflation of the balloon to obtain PAOP caused no statistically significant change in LAP or carotid flow, and PAOP was identical to both LAP and PWP. (PWP was determined by advancing and wedging the pulmonary artery catheter tip into a peripheral branch without inflating the balloon.(ABSTRACT TRUNCATED AT 250 WORDS)

Underestimation of prosthetic mitral valve areas: role of transseptal catheterization in avoiding unnecessary repeat mitral valve surgery

In patients with symptoms of heart failure after mitral valve replacement, identification of a stenosed prosthesis may be difficult. Twelve such patients were evaluated, presenting at a mean of 8.4 years after mitral valve replacement (four mechanical, eight porcine). Transvalvular pressure gradients were obtained using both indirect (pulmonary capillary wedge) and direct (transseptal catheterization) measurements of left atrial pressure. In all 12 patients, the diastolic gradient across the prosthetic valve was overestimated when pulmonary wedge rather than transseptal measurements were used. Calculated mitral valve prosthetic area was underestimated by the pulmonary wedge determinations. These findings may be caused by either the phase delay of the pulmonary wedge V wave relative to the transseptal V wave, resulting in a higher diastolic mean left atrial pressure, or the faulty wedge determinations in the setting of pulmonary hypertension, or both. In patients being considered for repeat mitral valve replacement because of prosthetic valve stenosis, transseptal catheterization allows for more accurate determination of prosthetic valve area and more accurately defines the need for repeat mitral valve surgery.

Increased pulmonary artery diastolic-pulmonary wedge pressure gradient after cardiopulmonary bypass

In 29 patients undergoing elective coronary artery bypass grafting, the diastolic pulmonary arterial pressure-pulmonary capillary wedge pressure gradient (DPAP-PCWP) and related haemodynamic parameters were determined before and after induction of anaesthesia, immediately after cardiopulmonary bypass (CPB) and one and three hours after CPB. The DPAP-PCWP gradient remained unchanged after induction of anaesthesia but was significantly increased after CPB. A gradient of 5 mmHg or greater was observed in 16 patients after CPB, whereas none of the patients showed such a gradient before CPB. A significant correlation was found between the change in DPAP-PCWP and the change in pulmonary vascular resistance (PVR). It is concluded that DPAP should not be used as a substitute of PCWP in the early postbypass period without frequent confirmation of the presence of the normal small DPAP-PCWP gradient. Since an increase of PVR may impair right ventricular ejection, we recommend the routine measurement of DPAP-PCWP gradient in the postbypass period.

Effect of nitroglycerin on the pulmonary venous gradient in patients after mitral valve replacement

Because the equality of the pulmonary artery wedge pressure and left atrial pressure has been questioned in patients with mitral valve disease and pulmonary hypertension, this study examined how vasomotor activity in the pulmonary capacitance vessels might contribute to a discrepancy between these pressures. The difference between the pulmonary wedge and left atrial pressures (designated as the pulmonary venous gradient) was measured after nitroglycerin administration in nine patients who had pulmonary hypertension (mean pulmonary artery pressure 40 mm Hg) after mitral valve replacement. Five minutes after sublingual nitroglycerin, 0.4 mg, the mean pulmonary wedge pressure decreased from 19 +/- 2 to 13 +/- 2 mm Hg (p less than 0.005), exceeding the decrease in left atrial pressure (15 +/- 2 to 11 +/- 2 mm Hg; p less than 0.005). Pulmonary blood flow increased from 4.6 +/- 0.4 to 4.9 +/- 0.4 liters/min (p less than 0.005). The decrease in mean pulmonary venous gradient from 4.0 +/- 0.8 to 1.7 +/- 0.6 mm Hg (p less than 0.025) was attributed to nitrate-mediated pulmonary venodilation. The ratio of venous gradient to blood flow, an index of pulmonary venous tone, decreased after nitroglycerin from 0.9 +/- 0.2 to 0.4 +/- 0.1 (p less than 0.01). These data indicate that reversible pulmonary vasoconstriction contributes to elevation of the pulmonary wedge pressure above the left atrial pressure in patients with chronic mitral valve disease and pulmonary hypertension and that nitroglycerin may produce pulmonary venodilation decreasing the pulmonary venous gradient.

Nitroglycerin therapy in the management of pulmonary hypertensive disorders

Vasodilator therapy has not been effective in patients with pulmonary hypertension because most of the drugs that have been utilized in treating this disorder do not exert selective effects on the pulmonary circulation. Nonselective agents may cause predominant systemic vasodilation and lead to severe hypotension; they may elicit reflex activation of the sympathetic nervous system and further elevate pulmonary artery pressures; or they may exert depressant effects on right ventricular function and aggravate right-sided heart failure. Nitroglycerin has theoretic appeal as a vasodilator drug in patients with pulmonary hypertension because it exerts a direct effect on the pulmonary circulation in doses that do not affect systemic resistance vessels or the myocardium and do not activate neurohumoral reflexes. Furthermore, the drug uniquely reduces pulmonary artery pressures in addition to pulmonary vascular resistance due to its ability to dilate venous capacitance vessels. Preliminary studies with sublingual and intravenous nitroglycerin in patients with pulmonary hypertension have shown that the drug produces marked hemodynamic improvement and that clinical benefits follow long-term therapy with transcutaneous or oral nitrates. However, treatment may provoke hypotensive events in some patients and systemic hypoxemia in others; still others may fail to benefit because the pulmonary vasculature is unresponsive to any vasodilator stimulus. Further work is needed to define the benefits and risks of nitroglycerin therapy in patients with pulmonary hypertension.