Pulmonary Vascular Steal in Chronic Thromboembolic Pulmonary Hypertension* Mitchell A. Olman, M.D.; William R. Auger, M.D., F.C.C.P.;t Peter F. Fedullo, M.D., F.C.C.P.; and Kenneth M. Moser, M.D., F.C.C.P.
After pulmonary thromboendarterectomy, performed for relief of chronic thromboembolic pulmonary hypertension, perfusion lung scans have frequently disclosed new perfusion defects in segments served by undissected pulmonary arteries. Our hypotheses were that these new postoperative defects occurred with great frequency and did not represent postoperative vessel occlusion. We retrospectively reviewed the preoperative and postoperative perfusion scans of 33 consecutive patients undergoing pulmonary thromboendarterectomy. New postoperative perfusion defects were noted in 23 of 33 patients. The incidence of new defects was
increased tenfold in segments that had (1) normal preoperative angiographic Gndings, (2) normal preoperative radionuclide perfusion, and (3) not been entered at the time of surgery. Postoperative angiograms, available in 15 of 33 patients, documented the nonembolic, nonocclusive nature of the new perfusion scan defects. The most plausible alternate explanation for this previously undescribed Goding is a redistribution of pulmonary arterial resistance induced by the thromboendarterectomy, namely, a pulmonary vas(Chest 1990; 98:1430-34) cular "steal."
groups have now shown that chronic, large Several vessel thromboembolic pulmonary hypertension
underwent pulmonary thromboendarterectomy at the University of California at San Diego Medical Center (UCSD) for chronic thromboembolic pulmonary hypertension between 1985 and 1988 and who met the following criteria were reviewed: {1) a standard six-view {anterior, posterior, right posterior oblique, left posterior oblique, right lateral, and left lateral) lung perfusion scan (3 mCi of technetium-labeled MAA, 500,000 counts per image) and a xenon ventilation scan• had been obtained preoperatively and before hospital discharge {two to three weeks after surgery); 2) right heart catheterization data and a pulmonary angiogram• had been obtained at UCSD preoperatively; {3) complete hemodynamic data were obtained during postoperative monitoring; the values provided are those obtained on the third or fourth postoperative day; {4) one of the authors was in the operating room at the time of surgery, reviewed the thrombus specimens and, with the surgeon, recorded the vessels entered at thromboendarterectomy. The lung perfusion scans were analyzed in the following manner. Using an anatomically derived template {Fig 1), 10• 11 the overall perfusion image in each projection was divided according to the template bronchopulmonary segmental boundaries. The perfusion to each anatomic segment was visually scored as normal {2.0), decreased {0.5 to 1.5), or absent {0). Only those segments with normal ventilation were ranked. Steal was noted to have occurred when a lung segment score decreased by 1.0 or more between the
is potentially correctable by surgical thromboendarterectomy. l-4 However, the postoperative course of these patients is complex, presenting management problems, including reperfusion edema, 5 persistent hypoxemia, pericardial effusion, and psychiatric disturbances.6 One unusual postoperative observation, seen in a significant number of our patients, has been the appearance of new perfusion defects in the postoperative lung scan.7 To our knowledge, this phenomenon has not been reported previously. These new defects appeared to occur, most commonly, in areas of the lung served by segmental and lobar arteries that had not been entered at surgical thromboendarterectomy. The analysis that follows was undertaken to determine the incidence of this phenomenon and its potential basis. The findings suggest that these new perfusion scan defects are due to postoperative redistribution of regional pulmonary vascular resistance, a phenomenon we have labeled pulmonary blood flow steal. METHODS
The medical records of 33 consecutive patients who successfully *From the Division of Pulmonary and Critical Care, Department of Medicine, University of California at San Diego. Presented in part at the annual meeting, American Federation for Clinical Research, Carmel, CA, February 6-9, 1990. Supported in part by NHLBI Institutional Research Training Award {HL-07022) and the UCSD-NHLBI SCOR in Acute Respiratory Failure {HL-23584). tWill Rogers Institute Research Fellow. Manuscript received April 30; accepted May 3. Reprint requests: Dr. Moser; UCSD Medical Center (H-772), 225 Dickinson Street, San Diego, CA 92103-1990
1430
Posterior view
FIGURE l. Anterior (left) and posterior (right) views of perfusion scan template that demonstrates the normal bronchopulmonary segmental anatomy. Similar diagrams were used to assess the lateral and oblique perfusion scan images. Pulmonary Vascular Steal (0/man et a/)
Table !-Preoperative and Postoperative Hemodynamic Data•
Preoperative Postoperative Hemodynamics Hemodynamics p Value PAP, Hg Cardiac output, Umin PVR, dyne-s/em•
41.7 ± 12 3.85 ± 1.1 789 + 420
24.2±6 5.9±1.0 200± 100
After pulmonary thromboendarterectomy, performed for relief of chronic thromboembolic pulmonary hypertension, perfusion lung scans have frequently disclosed new perfusion defects in segments served by undissected pulmonary arteries. Our hypotheses were that these new postoperative defects occurred with great frequency and did not represent postoperative vessel occlusion. We retrospectively reviewed the preoperative and postoperative perfusion scans of 33 consecutive patients undergoing pulmonary thromboendarterectomy. New postoperative perfusion defects were noted in 23 of 33 patients. The incidence of new defects was
increased tenfold in segments that had (1) normal preoperative angiographic Gndings, (2) normal preoperative radionuclide perfusion, and (3) not been entered at the time of surgery. Postoperative angiograms, available in 15 of 33 patients, documented the nonembolic, nonocclusive nature of the new perfusion scan defects. The most plausible alternate explanation for this previously undescribed Goding is a redistribution of pulmonary arterial resistance induced by the thromboendarterectomy, namely, a pulmonary vas(Chest 1990; 98:1430-34) cular "steal."
groups have now shown that chronic, large Several vessel thromboembolic pulmonary hypertension
underwent pulmonary thromboendarterectomy at the University of California at San Diego Medical Center (UCSD) for chronic thromboembolic pulmonary hypertension between 1985 and 1988 and who met the following criteria were reviewed: {1) a standard six-view {anterior, posterior, right posterior oblique, left posterior oblique, right lateral, and left lateral) lung perfusion scan (3 mCi of technetium-labeled MAA, 500,000 counts per image) and a xenon ventilation scan• had been obtained preoperatively and before hospital discharge {two to three weeks after surgery); 2) right heart catheterization data and a pulmonary angiogram• had been obtained at UCSD preoperatively; {3) complete hemodynamic data were obtained during postoperative monitoring; the values provided are those obtained on the third or fourth postoperative day; {4) one of the authors was in the operating room at the time of surgery, reviewed the thrombus specimens and, with the surgeon, recorded the vessels entered at thromboendarterectomy. The lung perfusion scans were analyzed in the following manner. Using an anatomically derived template {Fig 1), 10• 11 the overall perfusion image in each projection was divided according to the template bronchopulmonary segmental boundaries. The perfusion to each anatomic segment was visually scored as normal {2.0), decreased {0.5 to 1.5), or absent {0). Only those segments with normal ventilation were ranked. Steal was noted to have occurred when a lung segment score decreased by 1.0 or more between the
is potentially correctable by surgical thromboendarterectomy. l-4 However, the postoperative course of these patients is complex, presenting management problems, including reperfusion edema, 5 persistent hypoxemia, pericardial effusion, and psychiatric disturbances.6 One unusual postoperative observation, seen in a significant number of our patients, has been the appearance of new perfusion defects in the postoperative lung scan.7 To our knowledge, this phenomenon has not been reported previously. These new defects appeared to occur, most commonly, in areas of the lung served by segmental and lobar arteries that had not been entered at surgical thromboendarterectomy. The analysis that follows was undertaken to determine the incidence of this phenomenon and its potential basis. The findings suggest that these new perfusion scan defects are due to postoperative redistribution of regional pulmonary vascular resistance, a phenomenon we have labeled pulmonary blood flow steal. METHODS
The medical records of 33 consecutive patients who successfully *From the Division of Pulmonary and Critical Care, Department of Medicine, University of California at San Diego. Presented in part at the annual meeting, American Federation for Clinical Research, Carmel, CA, February 6-9, 1990. Supported in part by NHLBI Institutional Research Training Award {HL-07022) and the UCSD-NHLBI SCOR in Acute Respiratory Failure {HL-23584). tWill Rogers Institute Research Fellow. Manuscript received April 30; accepted May 3. Reprint requests: Dr. Moser; UCSD Medical Center (H-772), 225 Dickinson Street, San Diego, CA 92103-1990
1430
Posterior view
FIGURE l. Anterior (left) and posterior (right) views of perfusion scan template that demonstrates the normal bronchopulmonary segmental anatomy. Similar diagrams were used to assess the lateral and oblique perfusion scan images. Pulmonary Vascular Steal (0/man et a/)
Table !-Preoperative and Postoperative Hemodynamic Data•
Preoperative Postoperative Hemodynamics Hemodynamics p Value PAP, Hg Cardiac output, Umin PVR, dyne-s/em•
41.7 ± 12 3.85 ± 1.1 789 + 420
24.2±6 5.9±1.0 200± 100
