|
In approximately 25% of patients evaluated at the University
of California, San Diego, pulmonary angioscopy is used
to supplement the information obtained from pulmonary
angiography. The pulmonary angioscope is a diagnostic
fiberop-tic device that was developed to visualize the
intima of central pulmonary arteries. It is inserted through
a vascular sheath inserted in a central vein and passed
through the right heart into the pulmonary artery under
fluoroscopic guidance. Inflation of a latex balloon affixed
to the tip of the angioscope results in obstruction of
blood flow in the artery and permits visualization of
the arterial intima. The most useful role for pulmonary
angioscopy is in identifying operative candidates whose
angiographic findings suggest limited disease.
Helical CT scanning has been used increasingly in the
screening of patients with suspected thromboembolic disease,
but its role in the evaluation of patients with chronic
throm-boemblic disease is not completely defined. CT features
sug-gestive of CTEPH include evidence of organized thrombus
lin-ing the pulmonary vessels in an eccentric or concentric
fashion, enlargement of the right ventricle and central
pulmonary arter-ies, variation in size of segmental arteries
(relatively smaller in the affected segments compared
with uninvolved segments), bronchial artery collaterals,
a mosaic perfusion pattern of the lung parenchyma, and
parenchymal changes compatible with infarcts.23 The absence
of these findings does not rule out sur-gically accessible
disease and further evaluation is warranted if CTEPH is
suspected. CT imaging has significant value in eval-uating
those patients who may have alternative causes of pulmonary
artery obstruction, including carcinoma, lym-phadenopathy,
fibrosing mediastinitis, and primary pulmonary vascular
tumors. In addition, CT imaging along with physiolog-ic
testing plays an important role in evaluating patients
with coexistent parenchymal lung disease, such as emphysema
or restrictive lung disease.
A critical, but sometimes difficult, distinction to make
is between patients with CTEPH and patients with other
forms of pulmonary hypertension who also have thrombus
lining the cen-tral pulmonary arteries. The presence of
centrally located thrombus on spiral CT scanning does
not uniformly confirm the diagnosis of CTEPH since this
radiologic finding has been documented in patients with
primary pulmonary hypertension and other chronic pulmonary
diseases.24,25 Presumably, these le-sions are due to in
situ thrombosis rather than pulmonary embolism. Endarterectomy
in these patients carries a substan-tial mortality risk
and is unlikely to provide hemodynamic ben-efit. Historical
information is typically helpful in establishing the correct
diagnosis and the perfusion scan is either normal or demonstrates
minimal abnormalities in this setting.
Surgical Selection
Pulmonary endarterectomy is considered in patients who
are symptomatic and have evidence of hemodynamic or ventilatory
impairment at rest or with exercise. Patients undergoing
surgery usually exhibit a preoperative pulmonary vascular
resistance greater than 300 dynes/sec/cm -5 , typically
in the range of 800- 1000 dynes/sec/cm -5 . 26 For those
with milder pulmonary hyper-tension, the decision to operate
is based on individual circum-stances. Some with mild
elevation in pulmonary pressures at rest may develop a
significant rise in pressure with exertion. While not
yet substantiated, it is suspected these elevated pres-sures
over a prolonged period of time contribute to the devel-opment
of small-vessel arteriopathy in the patent vascular bed.
Some patients may elect to undergo surgery at this early
stage of disease because of dissatisfaction with their
exercise limita-tion or concerns about clinical deterioration
in the future. Those who choose not to pursue surgical
intervention at this stage of their disease require close
monitoring for progression of pul-monary hypertension.
Thromboendarterectomy is also consid-ered in patients
with normal or nearly normal hemodynamics with significant
involvement of one pulmonary artery, those with lifestyles
that involve vigorous activity (eg athletes), and those
who live at higher altitude. Dyspnea in these patients
is a func-tion of elevated dead space and minute ventilation
require-ments and suboptimal cardiac output with higher
level exercise.
Operability is determined by the location and extent
of prox-imal thromboemboli. The experience of the surgical
team will determine what is considered surgically accessible.
Thrombi must involve the main, lobar, or proximal segmental
arteries; disease originating more distally is not accessible
with current endarterectomy techniques. Crucial to determining
surgical candidacy and predicting operative outcome is
determining whether the amount of surgically accessible
thrombus is com-patible with the degree of hemodynamic
impairment. This is particularly true in patients with
severe preoperative pulmonary hypertension and right ventricular
dysfunction. Failure to sig-nificantly reduce the pulmonary
vascular resistance with endarterectomy, usually a result
of secondary small-vessel arte-riopathy, is associated
with a greater perioperative mortality rate and a worse
long-term outcome.27
The assessment of comorbid conditions is the next step
in preoperative surgical evaluation. Severe left ventricular
dysfunc-tion is the only absolute contraindication to
pulmonary throm-boendarterectomy. Advanced age, severe
right ventricular dys-function, and other significant
comorbid illnesses increase the perioperative morbity
and mortality, but these do not preclude surgical consideration.
Pediatric patients and octogenarians, as well as those
with complex coexistent disease have successfully undergone
the surgical procedure.28 Patients at risk for coro-nary
atherosclerotic disease should undergo coronary angiogra-phy
preoperatively and coronary artery bypass grafting or
valve replacement can be performed at the time of endarterectomy.
Referring for Pulmonary
Endarterectomy
Since surgery has the potential to substantially improve
symp-toms and pulmonary hemodynamics and the long-term
outcome is poor in medically treated patients, pulmonary
thromboen-darterectomy should be considered in any patient
once the diagnosis of CTEPH is made. Prior to surgery,
most patients are in New York Heart Association functional
class III or IV but postoperatively are in class I or
II and able to resume normal activities.29 Approximately
2000 endarterectomy procedures have been performed worldwide,
with roughly 1500 of them done at one center. In a review
of surgical series published since 1996, perioperative
mortality rates ranged from 5% to 24%, with significant
variation in hemodynamic improvement reported.1 Given
the high risk of pulmonary endarterectomy, patients should
be referred to centers that are able to provide a multidisciplinary
team with experience in the details of the evaluation
and treatment of chronic thromboembolic disease. Since
perioperative morbidity and mortality are significantly
influenced by the degree of right ventricular dysfunction
and the presence of secondary small-vessel vasculopathy,
surgical intervention is best pursued sooner in the disease
process rather than waiting until the patient suffers
from significant clinical and hemodynamic impairment.
Patients who are not candidates for thromboendarterectomy,
and those who suffer from significant residual pulmonary
hyper-tension following surgery, should be considered
for lung trans-plantation. Long-term treatment with epoprostenol
may also be of benefit in selected patients.30 The long-term
efficacy of prostacyclin analogs, endothelin-receptor
antagonists, and sildenafil has yet to be determined.
References
1. Fedullo PF, Auger WR, Kerr KM, et al. Chronic thromboembolic
pul-monary
hypertension. N Engl J Med 2001;345:1465-72.
2. Ryu JH, Olson EJ, Pellika PA. Clinical recognition
of pulmonary
embolism: problem of unrecognized and asymptomatic cases.
Mayo Clin
Proc 1998;73:873-79.
3. Dalen JE, Banas JS Jr, Brooks HL, et al. Resolution
rate of acute pul-monary
embolism in man: an angiographic study. N Engl J Med
1969;280:1194-99.
4. Wartski M, Collignon MA. Incomplete recovery of lung
perfusion after
3 months in patients with acute pulmonary embolism treated
with
antithrombotic agents. J Nucl Med 2000;41:1043-48.
5. Ryan KL, Fedullo PF, Davis GB, et al. Perfusion scan
findings under-state
the severity of angiographic and hemodynamic compromise
in
chronic thromboembolic pulmonary hypertension. Chest 1988;93:1180-
85.
6. Auger WR, Permikul P, Moser KM, et al. Lupus anticoagulant,
heparin
use, and thrombocytopenia in patients with chronic thromboembolic
pul-monary
hypertension: a preliminary report. Am J Med 1995;99:392-6.
7. Wolf M, Boyer-Neumann C, Parent F, et al. Thrombotic
risk factors in
pulmonary hypertension. Eur Respir J 2000;15:395-9.
8. Moser KM, Auger WR, Fedullo PF, et al. Chronic thromboembolic
pul-monary
hypertension; clinical picture and surgical treatment.
Eur Respir
J 1992;5:334-42.
9. Rich S, Levitsky S, Brundage BH. Pulmonary hypertension
from
chronic thromboembolism. Ann Intern Med 1988;108:425-34.
10. Olman MA, Marsh JJ, Lang IM, et al. Endogenous fibrinolytic
system
in chronic large-vessel thromboembolic pulmonary hypertension.
Circulation 1992;86:1241-8.
11. Lang IM, Marsh JJ, Olman MA, et al. Parallel analysis
of tissue-type
plasminogen activator and type 1 plasminogen activator
inhibitor in plas-ma
and endothelial cells derived from patients with chronic
pulmonary
thromboemboli. Circulation 1994:90:706-12.
12. Moser KM, Bloor CM. Pulmonary vascular lesions occurring
in
patients with chronic major vessel thromboembolic pulmonary
hyperten-sion.
Chest 1993;103:685-92.
13. Riedel M, Stanek V, Widimsky J, et al. Longterm follow-up
of
patients with pulmonary thromboembolism. Late prognosis
and evolution
of hemodynamic and respiratory data. Chest 1982;81:151-8.
14. Lewczuk J, Piszko P, Jagas J, et al. Prognostic factors
in medically
treated patients with chronic pulmonary embolism. Chest
2001;119:
818-23.
15. Auger WR, Moser KM. Pulmonary flow murmurs: a distinctive
physi-cal
sign found in chronic pulmonary thromboembolic disease.
Clin Res
1989;37:145A.
16. Simonneau G, Azarian R, Brenot F, et al. Surgical
management of
unresolved pulmonary emboli: a personal series of 72 patients.
Chest
1995;107:52S-55S.
17. Morris TA, Auger WR, Ysreal MZ, et al. Parenchymal
scarring is asso-ciated
with restrictive spirometric defects in patients with
chronic throm-boembolic
hypertension. Chest 1996;110:399-403.
18. Kapitan KS, Clausen JL, Moser KM. Gas exchange in
chronic throm-boembolism
after pulmonary thromboendarterectomy. Chest 1990;98:
14-9.
19. Menzel T, Wagner S, Kramm T, et al. Pathophysiology
of impaired
right and left ventricular function in chronic embolic
pulmonary hyper-tension:
changes after pulmonary thromboendarterectomy. Chest
2000;118:897-903.
20. Moser KM, Page GT, Ashburn WL, et al. Perfusion lung
scans provide
a guide to which patients with apparent primary pulmonary
hypertension
merit angiography. West J Med 1988;148:167-70.
21. Pitton MB, Dubeer C, Mayer E, et al. Hemodynamic effects
of non-ionic
contrast bolus injection and oxygen inhalation during
pulmonary
angiography in patients with chronic major vessel thromboembolic
pul-monary
hypertension. Circulation 1996;94:2485-91.
22. Auger WR, Fedullo PF, Moser KM, et al. Chronic major
vessel throm-boembolic
pulmonary artery obstruction: appearance at angiography.
Radiology 1992;182:393-8.
23. King MA, Ysreal M, Bergin CJ. Chronic thromboembolic
pulmonary
hypertension: CT findings. AJR Am J Roentgenol 1998;170:955-60.
24. Moser KM, Fedullo PF, Finkbeiner WE, et al. Do patients
with pri-mary
pulmonary hypertension develop extensive central thrombi?
Circulation 1995;91:741-5.
25. Russo A, De Luca M, Vigna C, et al. Central pulmonary
artery lesion
in chronic obstructive pulmonary disease: a transesophageal
echocardiog-raphy
study. Circulation 1995;91:741-5.
26. Hartz RS. Surgery for chronic thromboembolic pulmonary
hyperten-sion.
World J Surg 1999;23:1137-47.
27. Daily PO, Dembitsky WP, Iverson S, et al. Risk factors
for pulmonary
thromboendarterectomy. J Thorac Cardiovasc Surg 1990;99:670-8.
28. Jamieson SW, Kapelanski DP. Pulmonary endarterectomy.
Curr Probl
Surg 2000;37:165-252.
29. Archibald CJ, Auger WR, Fedullo PF, et al. Long-term
outcome after
pulmonary thromboendarterectomy. Am J Respir Crit Care
Med
1999;160:523-8.
30. McLaughlin VV, Genthner DE, Panella MM, et al. Compassionate
use
of continuous prostacyclin in the management of secondary
pulmonary
hypertension: a case series. Ann Intern Med 1999;130:740-3.
|
