is a life-threatening illness that is often misdiagnosed and

underrecognized. It is characterized by a single or recurrent

pulmonary thromboemboli that obstruct or obliterate the

pulmonary vascular bed as organized tissue, promoting

increased pulmonary vascular resistance and progressive

pulmonary hypertension and right-heart failure.

involvement of pulmonary microvascular changes in the

form of generalized pulmonary hypertensive arteriopathy

has been defined relatively recently and is gaining increased

recognition as a contributor to disease progression in

CTEPH.

course of disease with progressive dyspnea on exertion,

hemoptysis and general clinical deterioration associated with

right-heart dysfunction. Nonspecific symptoms and lack of

medical history of previous venous thromboembolism (VTE)

often complicate accurate diagnosis and, as a result, CTEPH

is frequently misdiagnosed and is underrecognized in clinical

practice.

70% among patients with a mean pulmonary artery pressure

>40 mm Hg, increasing to 90% at >50 mm Hg.

the occurrence of CTEPH in patients diagnosed with acute

pulmonary embolism (PE) has been considered rare. Data

from autopsy studies estimated the incidence of CTEPH at

1-3% overall and at 0.1-0.5% in patients surviving acute

PE. Every year in the United States, approximately 600 000

individuals suffer an acute pulmonary embolic event and that

the annual number of new CTEPH cases in the United States

is between 500 and 2500. This may underestimate the true

frequency of CTEPH because the disease is often misdiagnosed

due to nonspecific symptoms and variable disease

course.

assessing symptomatic CTEPH in patients with acute PE but

without prior VTE recently estimated the cumulative incidence

of CTEPH to be 1.0% 6 months after PE, 3.1% after 1 year

and 3.8% after 2 years and overall post-PE incidence are

approximately 3%.

hypertension is often identified during diagnostic work-up

in patients with unexplained pulmonary hypertension, many

of whom lack medical history suggesting previous VTE. In

a recent study of 142 consecutive patients with CTEPH, 90

(63%) had no previous history of symptomatic VTE.--------------------------