Cardiovascular Function In Severe Emphysema

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Several of the cited studies indicate that in emphysema, cardiovascular function is more limited depending on the more severe the airflow obstruction. Hence, one would expect to see the most severe limitation in patients who are candidates for either lung transplantation or lung volume reduction because these procedures are generally reserved for the most severely ill patients.

Cardiovascular Function in Patients Undergoing Lung Transplantation

Recently published guidelines for selection of patients requiring single or double lung transplantation for refractory COPD include subjects 65 yr of age or younger, whose FEV1 is 25% of predicted or lower. Other factors include the absence of significant hypercapnia, (PaCO2 r 55 mm Hg), and significant secondary pulmonary hypertension (66). This last exclusionary criterion is particularly important because of the increased incidence of intra- and perioperative complications in patients undergoing transplantation in the setting of severe pulmonary hypertension, even though successful transplantation can alleviate pulmonary hypertension in the long run. Hence, these patients should not have severe cor pulmonale, with irreversible right heart failure. In many centers, more leeway is allowed in younger patients (age < 55 yr).

Patients with end-stage obstructive lung disease who qualify for lung transplantation commonly have only mild-to-moderate pulmonary hypertension, producing variable degrees of RV dysfunction. Causes of pulmonary hypertension in these patients include destruction of pulmonary vascular space, with or without associated chronic hypoxemia and hypercapnia. Keller et al. (67) studied the hemodynamic profile at rest and during maximum exercise in 30 patients listed for lung transplantation, 15 chronic smokers and 15 with | -1-antitrypsin deficiency ( -1-ATD). Pulmonary function tests in both groups showed severe airflow obstruction (mean FEV1 < 25% predicted) and hyperinflation with impaired diffusion capacity. Both groups showed resting pulmonary hypertension, which was more severe with | -1-ATD (in COPD, PA systolic pressure = 33 + 5 mmHg, in | -1-ATD PA systolic pressure= 43+ 13 mmHg; p < 0.01) . With exercise, both groups showed similarly significantly increased PA pressures. Both groups also had abnormally increased PVR at rest and during exertion. One caveat regarding the interpretation of the data is that as discussed earlier, during exercise, patients with obstructive airways disease develop increased end-expiratory intrathoracic pressures. The degree to which increased intrathoracic pressure contributed to increased vascular pressures in these, and many other studies of exercise, pulmonary hemodynamics in COPD cannot determined. Nevertheless, it was interesting that even though indices of airflow obstruction were simi lar between the groups, the more extensive and homogeneous parenchymal destruction associated with | -1-ATD was associated with more severe resting pulmonary hypertension.

Right Ventricular Function in Patients with Severe COPD Evaluated for Lung Transplantation

Several techniques have been described to evaluate RV function in patients selected for single or double lung transplantation. These include echocardiography, ultrafast computerized tomography, first-pass multigated acquisition scan (MUGA), and direct measurement of RV ejection fraction, with RV end-diastolic and systolic volumes using a fast-thermistor-tipped PA catheter (68-70). Keller et al. (70) assessed RV function in 10 patients who were candidates for single-lung transplantation (SLT) diagnosed with severe COPD. Hemodynamic variables and measurements of RV function are described in Table 2. The exercise response was similar to the groups previously described. Pulmonary vascular resistance was elevated at rest and failed to decrease normally with exercise.

Estimated RV ejection fraction (RVEF) was significantly higher when measured using the single-pass MUGA technique than when measured by PA catheter (see Table 2). The differences between estimates of RVEF using MUGA vs thermodilution catheter are likely a result of systematic differences in the techniques. The MUGA scan essentially measures the capacity of the RV to empty during systole, whether blood is ejected forward into the PA, or backward, into the right atrium because of tricuspid regurgitation. Therefore, patients with normal or elevated RVEF by MUGA could have either normal RV function, or severely diminished RV function with concomitant tricuspid regurgitation (71,72) allowing for total RV emptying to be preserved. On the other hand, RVEF measured by a fast-thermistor-tipped PA catheter depends on sensing temperature changes in the PA over time to calculate cardiac output (CO) and stroke volume (SV) by thermodilution technique. Thus, whereas the MUGA RVEF better estimates the "total" volume ejected from the right ventricle (forward volume plus the volume ejected backward through the tricuspid valve), the catheter-measured RVEF best reflects effective "forward" volume ejected into the PA. Because many patients with advanced chronic lung disease and secondary pulmonary hypertension have RV dilation and tricuspid regurgitation, the MUGA estimation of RVEF is expected to be greater than the catheter-measured RVEF (69,70).

When SLT was first used in the management of patients with COPD and primary pulmonary hypertension, there was concern that patients

Table 2

Right Ventricular Function in Patients with Severe COPD Evaluated for Lung Transplantation

Table 2

Right Ventricular Function in Patients with Severe COPD Evaluated for Lung Transplantation

Variable

Rest

Exercise

P value (2 tail)

MUGA RVEF%

57 ± 10%

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