Ivabradine in systemic sclerosis related pulmonary arterial hypertension

Understanding and managing cardiac involvement in systemic sclerosis

INTRODUCTION

Cardiac involvement is common in systemic sclerosis occurring in up to 80% of patients. Primary myocardial dysfunction results from impairment of coronary microvascular circulation, myocardial inflammation and fibrosis with the prevalence of atherosclerosis remaining contradictory.

AREAS COVERED

This review presents the various aspects of cardiac involvement in SSc from a pathophysiological, clinical, diagnostic and therapeutic standpoint. Imaging modalities with emerging role in the understanding of mechanisms and prompt diagnosis of myocardial fibrosis namely cardiac magnetic resonance are also discussed.

EXPERT OPINION

Cardiac involvement in SSc - and particularly primary myocardial disease - remains a challenge as clinical symptoms manifest in advanced stages of heart failure and convey poor prognosis. Over the last years the introduction of sophisticated imaging methods of myocardial function has resulted in a better understanding of the underlying pathophysiological processes of myocardial damage such as microvasculopathy, inflammation, diffuse or focal fibrosis. Such developments could contribute to the identification of patients at higher risk for subclinical heart involvement for whom diligent surveillance and prompt initiation of therapy with cardioprotective and/or immunosuppressive drugs coupled with invasive interventions namely radiofrequency ablation, implantable cardioverter-defibrillator when indicated, may improve long-term outcomes.

Update on systemic sclerosis

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by autoantibody production, small-vessel vasculopathy, and skin and other organ fibrosis. The disease is clinically heterogeneous with most patients having some degree of skin sclerosis with varying organ system involvement. Early disease can be difficult to diagnose, especially with minimal skin sclerosis and absence of anti-nuclear antibody (ANA) positivity; however, studies have demonstrated early diagnosis is important as early treatment could potentially lead to better outcomes. New classification criteria have recently been published that have higher sensitivity for detecting early disease thus allowing for a broader spectrum of patients to be represented in clinical trials. Treatment guidelines have been published based on a limited number of randomized-controlled clinical trials; however, there are ongoing phase II and III clinical trials with novel agents that are promising and will change the treatment landscape over the next decade.

Strong linear relationship between heart rate and mean pulmonary artery pressure in exercising patients with severe precapillary pulmonary hypertension

The contribution of heart rate (HR) to pulmonary artery hemodynamics has been suggested in pulmonary hypertension (PH). Our high-fidelity pressure, retrospective study tested the hypothesis that HR explained the majority of mean pulmonary artery pressure (mPAP) and pulse pressure (PApp) variation in 12 severe precapillary PH patients who performed incremental-load cycling while in the supine position. Seven idiopathic pulmonary arterial hypertension patients and five chronic thromboembolic PH patients were studied. Four to five PAP-thermodilution cardiac output (CO) points (mean: 4.4) were obtained. At rest, mPAP was 57 ± 9 mmHg, PApp was 51 ± 11 mmHg, HR was 90 ± 12 beats/min, and stroke volume (SV) was 50 ± 22 ml. At peak exercise, mPAP was 76 ± 10 mmHg, PApp was 67 ± 11 mmHg, and HR was 123 ± 18 beats/min (i.e., 71 ± 10% of maximum HR, each P < 0.05), whereas SV was 51 ± 20 ml ( P = not significant). The input resistance did not change (mPAP/CO = 14.1 ± 4.1 vs. 13.5 ± 4.4 mmHg·min·l−1). The relative increase in mPAP was related to the relative increase in HR ( n = 12, r2 = 0.74) but not in CO. mPAP was linearly related to CO in 8 of 12 patients (median r2 = 0.83) and to HR in 12 of 12 patients (median r2 = 0.985). The parsimony principle favored the latter fit. PApp was linearly related to mPAP in 12 of 12 patients (median r2 = 0.985), HR in 10 of 12 patients (median r2 = 0.97), CO in 7 of 12 patients (median r2 = 0.87), and SV in 1 of 12 patients. A strong linear relationship between HR and mPAP was consistently documented in severe precapillary PH patients who performed supine exercise. The limited value of thermodilution CO to predict mPAP could be explained by unavoidable precision errors in CO measurements, unchanged/decreased SV on exercise, curvilinearity of the mPAP-CO relationship at high flow, or flow-independent additional mechanisms increasing mPAP on exercise.