Obesity Linked to Improved Survival of Patients with Pulmonary Hypertension

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In patients who have heart failure with preserved ejection fraction, concurrent pulmonary hypertension (PH) is associated with worse survival. Conversely, obesity in patients with heart failure confers a better prognosis, a phenomenon known as the "obesity paradox." Whether obesity influences survival in patients with PH has been unclear.

In a previous study published in the Journal of the American Heart Association, researchers at Massachusetts General Hospital found evidence suggesting that PH contributes to the pathophysiology of metabolic heart disease. A new study by a team of Mass General trainees including Rachel Frank, MD, a current cardiology fellow, together with Jennifer E. Ho, MD, cardiologist in the Heart Failure and Transplant Program and the Cardiovascular Research Center at Mass General, and colleagues was published in in the Journal of the American Heart Association. This study extended those findings by demonstrating a direct association between body mass index and PH with obesity modifying the effect of PH on mortality.

Study Details

The researchers examined the records of 8,940 patients at Mass General, ages 18 to 80, who underwent clinically indicated right-sided heart catheterization between 2005 and 2016. Hemodynamic measures obtained at the time of the procedure included mean pulmonary artery (PA) pressure (mPAP) and pulmonary capillary wedge pressure (PCWP).

The research team used the following definitions:

• PH = mPAP >20 mm Hg
• Transpulmonary gradient (TPG) = mPAP minus PCWP
• Subtypes of PH:
  • Precapillary = PCWP ≤15 mm Hg and TPG ≥12 mm Hg
  • Postcapillary = PCWP >15 mm Hg and TPG <12 mm Hg
  • Mixed = PCWP >15 mm Hg and TPG ≥12 mm Hg

BMI and PH

52% of the 5,512 nonobese patients and 69% of the 3,428 obese patients had PH. The prevalence of PH increased with increasing BMI, from 51% among the nonobese patients to 79% among patients with BMI >40 kg/m2. Overall, obesity was associated with a 34% greater overall odds of PH (P < 0.001).

PH and Mortality

Over an average follow-up period of 5.5 years, 2,536 patients died. PH doubled the risk of all-cause mortality (P < 0.001) independent of a history of heart failure. The risk was increased regardless of PH subtype (P < 0.001 for all three subtypes).

Obesity and Mortality

Among patients with both PH, those with concomitant obesity had a 23% lower risk of death than their nonobese counterparts (P < 0.001). Further analysis showed that the effect was limited to patients with precapillary or postcapillary PH:

• Precapillary PH and obesity — HR, 0.57; P < 0.001
• Postcapillary PH and obesity — HR, 0.81; P = 0.009
• Mixed PH and obesity — HR, 0.87; P = 0.13

Obesity modified the effect of precapillary PH on mortality (P for interaction = 0.02), although not that of postcapillary PH. This study thus supports an association between obesity and PH that is akin to the obesity paradox observed in heart failure.

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