Feeling the Pressure

Feb 26 2020

In the GIM clinic today, I saw a patient who was been followed for findings of elevated RVSP on echocardiogram. He had symptoms of dyspnea with exertion, but was otherwise asymptomatic. We questioned the presence of pulmonary hypertension, however had no clear cause based on his current presentation and investigations. I always have difficulty remembering the classification for pulmonary hypertension, and so this was a great opportunity for me to review this topic.

Pulmonary hypertension (PH) is defined as a mean pulmonary artery pressure ≥ 25 mmHg. Clinically, PH is a pathophysiological disorder that may involve multiple clinical conditions. The WHO classification describes 5 groups of pulmonary hypertension:

• Group 1: Pulmonary artery hypertension (PAH). This develops due to an occlusive vasculopathy of the pulmonary arterioles, which may be idiopathic or associated with several disease states. Commonly associated conditions include: connective tissue diseases (scleroderma, lupus), congenital heart disease, portal hypertension, HIV or schistosomiasis infections, and drugs.
• Group 2: PH due to left heart disease. This develops due to chronically elevated left atrial pressure, which causes PH by a passive retrograde transmission of pressure. Causes include left ventricular systolic/diastolic dysfunction, and aortic or mitral valve disease.
• Group 3: PH due to lung diseases and/or hypoxia. This develops in patients with lung disease (COPD, interstitial lung disease), sleep disordered breathing, or other abnormalities of blood gases (hypoventilation, high altitude). Hypoxic pulmonary vasoconstriction (a normal physiologic response), loss of pulmonary capillary cross-sectional area, and pulmonary vascular remodeling can all be contributing factors.
• Group 4: Chronic thromboembolic PH. Approximately 3% of patients with acute pulmonary embolism go on to develop obstructive pulmonary arterial remodeling resulting in PH. These patients are often found to have an underlying thrombophilic disorder.
• Group 5: PH with unclear and/or multifactorial mechanisms. This is a diverse group of PH etiologies. Hematologic disorders (such as chronic hemolytic anemia), systemic disorders (such as sarcoidosis), metabolic disorders (such as glycogen storage diseases), and others may cause PH by unclear and/or multifactorial mechanisms.

For our patient, there was no obvious explanation for his elevated RVSP. He had no history of conditions associated with Group 1 PH, such as connective tissue disease, congenital heart disease or past infections, however could still have idiopathic PAH. His exam and echocardiogram showed no evidence of left ventricular or valvular disease, ruling out Group 2. There was no history of PE or thromboembolic disease, and no evidence of any systemic diseases, excluding Groups 4 and 5. We decided to send him for pulmonary function testing to assess for any underlying lung disease for Group 3 PH. His PFT will also determine his DLCO which will help in the diagnosis (DLCO is reduced in PH and an isolated reduction in DLCO is a typical finding in Group 1 PH). This case allowed me to gain a better understanding of pulmonary hypertension, the various classifications, and how to approach a patient with PH in the future.

-MB-

References:

1. Simonneau G, Gatzoulis MA, Adatia I, et al. Updated Clinical Classification of Pulmonary Hypertension. Journal of the American College of Cardiology 2013; 62(25): 35-41.