SEPARATING THE 'RIGHT FROM THE LEFT'
IN PATIENTS WITH PULMONARY HYPERTENSION
PAUL R. FORFIA, M.D.

Pulmonary hypertension (PH) is a heterogeneous condition that may be due to a primary pulmonary vasculopathy (Group I; pulmonary arterial hypertension or PAH), or may be secondary to left heart disease and pulmonary venous hypertension (PVH: Group II), chronic respiratory conditions (Group III), prior pulmonary emboli (Group IV) or miscellaneous or multifactorial causes (Group V) (1). These are necessary distinctions for appropriate diagnosis and treatment of PH. This is especially true when discerning PAH from PVH, as PH specific therapy (i.e. prostaclyins, endothelin receptor blockade) is intended only for patients with PAH, and will have either no effect, or possibly exacerbate the condition of a patient with left heart disease.

Patients with pulmonary vascular disease (i.e. PAH) and patients with PVH will both present with dyspnea on exertion as their most common complaint. On initial echo-Doppler examination, both groups will often have normal LV systolic function (i.e. normal LV ejection fraction) and PH. Thus, patients will often 'look the same' on initial, superficial assessment. However, this can be very misleading, as more thorough clinical assessment will often reveal marked phenotypic differences between the PAH and PVH patient.

Table 1 highlights some of the common distinguishing clinical and echo-Doppler features between the 'left sided' and 'right sided' PH patient. Exertional angina and syncope are clinical clues to PAH, as are the relative absence of common conditions such as hypertension and atrial fibrillation. PAH patients will have a preponderance of findings to suggest right heart disease on exam and ECG. Although more severe PH can point to PAH over PVH, there is significant overlap between the two conditions, and the limited accuracy of Doppler pressure estimation makes this an unreliable differentiating feature (2). Patients with PVH most often have left ventricular hypertrophy and left atrial enlargement, while patients with PAH very often possess the triad of RV enlargement, RV dysfunction, and septal bowing (3-5).

Definitive hemodynamic assessment requires right heart catheterization. However, hemodynamic assessment, and particularly pulmonary artery wedge pressure (PAWP) measurement is prone to error in patients with PH, which can lead to misdiagnosis and therapy. The PAWP is commonly underestimated in the obese patient due to failure to measure the PAWP at end-expiration-this can lead to a false diagnosis of PAH. The PAWP can also be overestimated by recording a partial occlusion pressure, leading to a false diagnosis of PVH, and a missed diagnosis of PAH (5). Misapplication of therapy in either scenario can have devastating consequences.

Differentiating 'left from right' in PH requires an integration of salient clinical and echo-Doppler features of the patient presentation, along with invasive hemodynamic assessment performed by an experienced operator. The noninvasive and invasive patient assessment should be viewed as complimentary approaches that will most often lead to the correct diagnosis.

Table 1

Definition of abbreviations: PND- paroxysmal nocturnal dyspnea; LVH-left ventricular hypertrophy; LAE-left atrial enlargement; RVH-right ventricular hypertrophy; RAE-right atrial enlargement; P2-pulmonic closure sound; MR-mitral regurgitation; MS-mitral stenosis; TR-tricuspid regurgitation; PASP-pulmonary artery systolic pressure.