(Surgical salvation or inappropriate aggression?)
The following chest x-ray and ECG are of a twenty-five year old
woman, who presented with worsening dyspnoea. She was still on
warfarin anticoagulation following a large pulmonary embolus one
year previously. Despite extensive work-up, there was no evidence
of underlying thrombophilia, and Doppler ultrasound of both lower
extremities had shown no evidence of venous thrombosis. Now, at this visit,
the woman had markedly limited effort tolerance.
Echocardiogram revealed right ventricular hypertrophy, and showed a sytolic pulmonary artery pressure of 106 mmHg. A ventilation scan was normal, but the perfusion scan was as follows:
Surgical Intervention!The appropriate intervention is pulmonary thromboendarterectomy . This is non-trivial surgery, and should probably still be restricted to the relatively few institutions (and surgeons) with the relevant expertise. In the best centres (UCSD) the peri-operative mortality is now under 9%, a significant figure, but still far better than relegating such patients to the ratbag of medical therapy. A recent report on 273 consecutive patients [Am J Respir Crit Care Med 1996 153 A92 {abstr}] gives an in-hospital mortality of 6.6%. Pre-operative work-up should include echocardiography, ventilation-perfusion scanning, and pulmonary angiography. Note that large pulmonary artery thrombi may be found in patients with pulmonary hypertension (presumed to be primary) without segmental or larger defects on perfusion scan. Such thrombi are thought not to be haemodynamically significant, and thromboendarterectomy in such cases is probably of no value [Circulation 1995 Feb 1;91(3):741-5] ! However, if there are segmental perfusion defects, then the severity of the perfusion defect correlates poorly with haemodynamic compromise, according to an earlier article from the same group [Chest 1988 Jun;93(6):1180-5] - rather confusing, really. Criteria for surgical selectionFairly well-defined criteria exist:
Surgical treatment involves deep hypothermic arrest, with complete removal of all thrombus from affected branches of the pulmonary arteries. Failure of surgery to correct the pulmonary hypertension is usually related to inadequate surgery, or recurrent thromboembolism. (It has also been suggested that post-operative outcome is better with avoidance of inotropes, vasodilators and high tidal volume ventilation, to limit reperfusion injury and possibly mortality [Anesth Analg 2000 Feb;90(2):267-73], but the design of the study doesn't allow us to distinguish the effects of these three variables). Alternative surgical strategies have been described that avoid the need for deep hypothermic arrest, but these have not been validated on large numbers of patients. Another possible curative surgical therapy for pulmonary hypertension is of course lung transplantation (or combined heart and lung transplantation), but this necessitates lifelong immune suppression, with substantial risks of opportunistic infection, and a 30% risk of bronchiolitis obliterans and rejection. For balloon angioplasty in those not amenable to surgery, see [ Circulation 2001 Jan 2;103(1):10-3]. Overall management of pulmonary hypertension of all types has fairly
recently been reviewed by Wanstall and Jeffery [Drugs, 1998 Dec 56(6) 989-1007],
which authors emphasise the use of oral calcium agonists or IV prostacyclin
for primary pulmonary hypertension (after showing a response to acute challenge
with a short-acting vasodilator), oxygen therapy for pulmonary hypertension
associated with chronic obstructive pulmonary disease, and surgery for
CTEPH.
Surgical OutcomesAs already mentioned, adequate surgery is usually curative. Six(+) year survival is reported by the UCSD group to be over 75% [Archibald et al, Am J Respir Crit Care Med 1999 160 523-8], although the nature of their survey (a postal questionnaire with a response rate of 73%) may have introduced bias - this is well-discussed by the authors. Ninety-three percent of the patients in the survey reported a New York Heart Association functional class of one or two. Many patients previously unable to work or live normal lifestyles reported a return to normal levels of activity. There are several caveats:
Apart from the risk of intra-operative mortality, there is a significant incidence of post-operative complications in ICU. One that has received some prominence (especially in cases such as the above one, with markedly diminished blood flow to one lung), is the risk of reperfusion injury to the lung. Unresolved Questions'CTEPH' seems to be a decidedly uncommon disorder (although we are sure that every year, thousands of patients die worldwide because they are denied surgery for the condition). Why should these patients not lyse their clots like other individuals?
Severity of pulmonary hypertension may not relate to the size of the thrombus - other factors may be responsible. Consider [Am J Respir Crit Care Med 2001 Jul 15;164(2):319-24] implicating Monocyte chemoattractant protein-1 (MCP-1), but is this cause or effect? Likewise for human angiopoietic gene expression (angiopoietin-1) [J Thorac Cardiovasc Surg 2001 Jul;122(1):65-73]. We would also be most interested in reports on the thromboelastogram in such patients. FootnoteThe patient briefly discussed above did well following pulmonary thrombo-endarterectomy. No reperfusion injury was seen, and pulmonary artery pressures dropped dramatically. (Parenthetically, we note that the surgery in this patient was performed in a third-world country by a surgeon with significant expertise in the operation. Ideally, such cases should of course be referred overseas to institutions with considerable experience in the surgical and peri-operative management of chronic thromboembolic pulmonary hypertension, but cost then becomes a major, and often prohibitive issue). |
Date of First Publication: 2001/10/14 | Date of Last Update: 2006/10/24 | Web page author: Click here |