Pulmonary capillary surface area in supine exercising humans: demonstration of vascular recruitment.

In exercising humans, cardiac output (CO) increases, with minor increases in pulmonary artery pressure (PAP). It is unknown if the CO is accommodated via distention of already perfused capillaries or via recruitment of nonconcomitantly perfused pulmonary capillaries. Ten subjects (9 female) performed symptom-limited exercise. Six had resting mean PAP (PAPm) <20 mmHg, and four had PAPm between 21 and 24 mmHg. The first-pass pulmonary circulatory metabolism of [3H]benzoyl-Phe-Ala-Pro (BPAP) was measured at rest and at peak exercise, and functional capillary surface area (FCSA) was calculated. Data are means ± SD. Mean pulmonary arterial pressure rose from 18.8 ± 3.3 SD mmHg to 28.5 ± 4.6 SD mmHg, CO from 6.4 ± 1.6 to 13.4 ± 2.9 L/min, and pulmonary artery wedge pressure from 14 ± 3.3 to 19.5 ± 5 mmHg (all P ≤ 0.001). Percent BPAP metabolism fell from 74.7 ± 0.1% to 67.1 ± 0.1%, and FCSA/body surface area (BSA) rose from 2,939 ± 640 to 5,018 ± 1,032 mL·min-1·m-2 (all P < 0.001). In nine subjects, the FCSA/BSA-to-CO relationship suggested principally capillary recruitment and not distention. In subject 10, a marathon runner, resting CO and FCSA/BSA were high, and increases with exercise suggested distention. Exercising humans demonstrate pulmonary capillary recruitment and distention. At moderate resting CO, increasing blood flow causes principally recruitment while, based on one subject, when exercise begins at high CO, further increases appear to cause distention. Our findings clarify an important physiologic question. The technique may provide a means for further understanding exercise physiology, its limitation in pulmonary hypertension, and responses to therapy.

Right ventricular ST-elevation myocardial infarction as a cause of death in idiopathic pulmonary arterial hypertension.

A 32-year-old woman with advanced idiopathic pulmonary arterial hypertension (PAH), treated with oral tadalafil and intravenous epoprostenol, presented with typical angina pectoris of one day's duration. Her electrocardiogram, previously typical of pulmonary hypertension, revealed an acute ST-elevation myocardial infarction in the anterior precordial leads. She had a prior coronary angiogram, in preparation for lung transplantation, that revealed normal coronary arteries. Urgent coronary angiography showed acute occlusion of several acute marginal coronary branches that feed the right ventricle (RV). Coronary angioplasty and stenting was unable to adequately restore coronary perfusion. Despite support, she developed progressive cardiogenic shock and died three days later. This is an unusual complication of PAH.

Cardiac output as a predictor in congenital heart disease: Are we stating the obvious?

BACKGROUND: Significant pulmonary regurgitation, declining right-sided ejection fraction, increased right ventricular (RV) volumes as well as left ventricular (LV) dysfunction have all been identified as predictors of poor outcomes in patients with congenital heart disease (CHD). The prognostic value of the cardiac output (CO) in these patients however has never been studied. METHODS: All consecutive ambulatory adult patients with CHD referred for magnetic resonance imaging (MRI) at the Montreal Children's Hospital between June 2007 and May 2009 were included. Right ventricular (RV) and left ventricular (LV) variables including end diastolic and end systolic volumes (EDV, ESV respectively), ejection fractions (EF) and regurgitant volumes were obtained. Cardiac index (CI) was calculated. Patients were followed for cardiac-related hospitalizations and cardiac interventions. RESULTS: Ninety-six patients were included. Median follow up was 3.9 ± 1.4 years. Nineteen percent of patients had a systemic CI<2.4 l/min/m(2). LVEDV, LVEF and RVEF were significantly diminished in the low CI group with a significant increase in RVESV and total regurgitant volume. Best predictors of low CI were LVEF (AUC=0.74), RVEF (AUC=0.71), total RV regurgitant volume (AUC=0.64) and RVESV (AUC=0.563). Low systemic CI was the best predictor of cardiac-related hospitalizations (hazard ratio 3.5, 95% confidence interval 1.5-8.5) and cardiac interventions (hazard ratio 2.2, 95% confidence interval 1.3-4.0), superior to LVEF, RVEF, total regurgitant volume and RVESV parameters. CONCLUSIONS: In patients with congenital heart disease, cardiac index is the best predictor of cardiac hospitalizations and cardiac interventions.

Perioperative management of patients with drug-eluting stents.

Thrombosis of a drug-eluting stent (DES) is a catastrophic complication. The risk of stent thrombosis (ST) is increased in the perioperative setting and is strongly associated with the cessation of antiplatelet therapy. This article reviews the perioperative management of patients with DES with a clinical focus on the perioperative use of antiplatelet therapy. Cessation of dual antiplatelet therapy is the single most significant predictor of perioperative ST. Available data on perioperative management of patients with DES are limited, and recommendations are therefore limited. To avoid ST with DES, aspirin and thienopyridines should ideally be continued throughout surgery. In spite of the increased risk of bleeding, this strategy is acceptable in many types of invasive surgical procedures with no change in outcome. However, if the bleeding risk outweighs the risk of ST, other potential strategies include treatment with aspirin alone, "bridging therapy" with aspirin and a glycoprotein IIb/IIIa inhibitor and/or heparin, and "bridging therapy" without aspirin. Novel antiplatelet therapies are promising and potentially valuable in the perioperative management of patients with DES. Maintaining dual antiplatelet therapy is the mainstay of perioperative ST prevention. However, short-term discontinuation of thienopyridines might be associated with relatively low risk if aspirin therapy is maintained perioperatively.