Up to 4% of patients surviving a pulmonary embolus will develop chronic thromboembolic pulmonary hypertension resulting from the formation of abnormal thrombus or ineffective thrombolysis.
Professor David McGiffin, a cardiothoracic surgeon at the Alfred Hospital in Melbourne, told the HAA meeting how pulmonary endarterectomy that requires complete circulatory arrest during surgery can cure the associated pulmonary hypertension. The procedure is now regarded as first-line therapy in selected patients.
“Chronic thromboembolic pulmonary hypertension (CTEPH) is an uncommon disease but important for several reasons,” he said.
“It is substantially under-recognised, can result in progressive and disabling symptoms, and the natural history is progression to death.”
Pulmonary endarterectomy can improve respiratory symptoms and prevent further deterioration.
The pathology of CTEPH involves the development of extensive fibrous blind pouches, bands and webs within the artery that obstruct pulmonary blood flow. This leads to secondary arteriolar vascular remodelling, pulmonary hypertension and detrimental right ventricular remodelling.
Detailed imaging is essential to define the extent and significance of the lesions, most importantly a ventilation-perfusion scan to detect perfusion defects.
A CT scan is needed to check for any large areas of infarcted lung which is unable to be restored by the operation and might limit the symptomatic benefit.
A pulmonary angiogram shows the extent of the thromboembolic disease, and guides the surgical strategy.
“The surgery is a major undertaking,” Professor McGiffin said.
It requires cardiopulmonary bypass, profound hypothermia which cools the core body temperature to 20oC, carotid artery perfusion to protect blood flow to the brain, and periods of intermittent circulatory arrest to stop blood flow in the pulmonary artery and allow a clear surgical field.
Professor McGiffin demonstrated a case, showing how careful blunt dissection of the thromboembolic scar tissue, branching down through several levels of arteries, extracted a tangled mass many centimetres long and restored normal blood flow.
“In experienced hands the mortality of the operation is between 1% and 5%,” he said.
“Mortality and morbidity is related to multisystem failure because of poor physical reserves and severe pre-operative subsystem dysfunction, reperfusion pulmonary injury, severe right ventricular failure, persistent severe pulmonary hypertension because of extensive pulmonary vascular remodelling and, rarely, pulmonary haemorrhage from perforation of the pulmonary artery wall.
“Long term survival of these patients is excellent and most have normalisation or near normalisation of their pulmonary artery pressures and rapid reverse remodelling of the dysfunctional right ventricle.”
Professor McGiffin said haematologists who were concerned about the progress of their patients after pulmonary embolism should refer to an experienced respiratory physician who could make the diagnosis of CTEPH and engage a specialist surgical team in the discussion when appropriate.