Key Point

At the annual ATS meeting, presenters debated the safety and accuracy of right heart catheterization for determining pulmonary artery pressure in patients with PAH. They also discussed the viability of echocardiography as a noninvasive alternative.

SAN DIEGO—It is accepted practice for patients thought to have pulmonary arterial hypertension (PAH) to undergo right heart catheterization before being treated. But is this gold-standard invasive test necessary in every case of suspected PAH?

Yes, asserted Ivan M. Robbins, MD, during a debate at the annual meeting of the American Thoracic Society.¹ With transthoracic echocardiography, the best available noninvasive test for PAH, there are too many opportunities for inaccuracy and omission, argued Dr. Robbins, Director of the Adult Pulmonary Hypertension Center at the Vanderbilt University Medical Center in Nashville.

RIGHT HEART CATHETERIZATION IS PRUDENT

Echocardiography’s inadequacy stems in part from the fact that the test indirectly estimates pulmonary artery systolic pressure. Also, it cannot measure pulmonary wedge pressure and does not permit calculation of pulmonary vascular resistance; a usable tricuspid regurgitation jet signal often cannot be obtained. “This is really a very operator-dependent test,” remarked Dr. Robbins.

Of the 10 studies that assessed the accuracy of echocardiography in estimating pulmonary artery systolic pressure, nine showed a statistically significant correlation with right heart catheterization findings; the correlation coefficients ranged from 0.57 to 0.95. However, these seemingly impressive statistics are misleading. Among individual patients, the disparity between echocardiography and right heart catheterization was as great as 60 mm Hg, Dr. Robbins related.

Another shortcoming of echocardiography is that it often does not accurately estimate left ventricular diastolic dysfunction, a key measure for differentiating PAH from pulmonary venous hypertension. According to Dr. Robbins, the most recent study to evaluate this prompted the conclusion that standard echocardiographic indices of diastolic dysfunction correlate poorly with left ventricular diastolic pressure transients. He added that echocardiography cannot replace right heart catheterization in clinical trials because it does not distinguish among the different types of PAH.

In closing, Dr. Robbins maintained that echocardiography cannot be used to guide PAH therapy. This may lead to inappropriate treatment resulting in clinical worsening, pulmonary edema, and even death, he warned. “Finally, the cost of PAH therapy is truly astronomical,” he said. “So if you do not have an accurate diagnosis and the patient does not really have PAH, this is a significant burden on the medical system.”

CATHETERIZATION IS NOT ALWAYS REQUIRED

Although most patients with suspected PAH undergo right heart catheterization before receiving treatment, the need for the procedure is not a given, countered Harold I. Palevsky, MD, Director of Pulmonary Vascular Disease at the University of Pennsylvania Medical Center in Philadelphia. Indeed, one must consider the risks of right heart catheterization, which have included one case each of ventricular tachycardia/ventricular fibrillation, persistent foramen ovale with cerebrovascular accident, and cerebral air embolism at Dr. Palevsky’s institution over the past five years.

“Routine right heart catheterization frequently will not be definitive and underestimates the degree of pulmonary vascular resistance,” Dr. Palevsky pointed out. The reason for this, he explained, is that most catheterizations are done with the patient at rest and supine, a state not necessarily representative of the hemodynamics of upright posture and activity.

In addition, the results are sometimes reported without important data such as the blood flow measurements needed to evaluate pulmonary vascular resistance. Inconsistent results can be a problem, as shown by the mean coefficient of variability of 8% among one group of 12 PAH patients who underwent right heart catheterization.

Thus, while the procedure is recommended to guide PAH therapy, the quality of the evidence to support that recommendation is considered low. Furthermore, the usefulness of invasive testing for pulmonary vasoreactivity to select the optimal PAH therapy is less clear now that novel oral and inhaled agents with vasodilatory and antiproliferative properties are available.

On the other hand, there are data showing that echocardiographic signals suitable for estimating right-sided cardiac pressures can be obtained in 95% of unselected cardiovascular patients, Dr. Palevsky claimed. And despite any discrepancies between echocardiographic and right heart catheterization findings, significant PAH is usually detected by both tests.

“Most studies report a high correlation—0.57 to 0.93—between transthoracic echocardiography and right heart measurement of pulmonary arterial systolic pressure,” he pointed out. Furthermore, the sensitivity and specificity of echocardiography for PAH range from 0.79 to 1.00 and 0.60 to 0.98, respectively.

Dr. Palevsky described one of his patients, a woman, age 65, with scleroderma and early class III functional status. Her echocardiographic findings included an estimated pulmonary artery systolic pressure of 70 mm Hg and good visualization of the right ventricle and tricuspid regurgitant jet.

This patient had no hypertension, left ventricular hypertrophy or diastolic dysfunction, or chest pain and has had a normal stress thallium study, said Dr. Palevsky. “With or without a right heart catheterization, we will treat her with an [endothelin-receptor antagonist],” he concluded.

—Timothy Begany

Reference
1. McLaughlin VV, Tapson VF, Robbins LM, et al. Pro-con debates in pulmonary arterial hypertension: right-heart catheterization is required in all patients prior to institution of PAH therapy. Presented at: annual meeting of the American Thoracic Society; May 24, 2005; San Diego, Calif.

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