Left atrial conduit function modulates right ventricular afterload, exercise capacity and survival in heart failure patients

Prognostic role of tricuspid annular plane systolic excursion/pulmonary artery systolic pressure ratio in patients hospitalized for acute heart failure

BACKGROUND

The role of TAPSE/PASP, a measurement of right ventricular to pulmonary artery coupling, in patients hospitalized for acute heart failure (AHF) is poorly described.

OBJECTIVES

To evaluate the prognostic impact of TAPSE/PASP in AHF.

METHODS

This retrospective single-center study included patients hospitalized for AHF between January 2004 and May 2017. TAPSE/PASP was evaluated as a continuous variable and as tertiles according to its value on admission. The main outcome was the composite of 1-year all-cause death or heart failure hospitalization.

RESULTS

A total of 340 patients were included [mean age 68.8 ± 11.8 years; 76.2% men, mean left ventricular ejection fraction (LVEF) 30.4 ± 13.3%]. Patients with lower TAPSE/PASP had more comorbidities and a more advanced clinical profile, and received higher doses of intravenous furosemide in the first 24 h. There was a significant, linear, inverse relationship between TAPSE/PASP values and the incidence of the main outcome (P = 0.003). In two multivariable analyses including clinical (model 1), biochemical and imaging parameters (model 2) TAPSE/PASP ratio was independently associated with the primary end point [model 1: hazard ratio 0.813, 95% confidence interval (CI) 0.708-0.932, P = 0.003; model 2: hazard ratio 0.879, 95% CI 0.775-0.996, P = 0.043]. Patients with TAPSE/PASP greater than 0.47 mm/mmHg had a significantly lower risk of the primary end point (model 1: hazard ratio 0.473, 95% CI 0.277-0.808, P = 0.006; model 2: hazard ratio 0.582, 95% CI 0.355-0.955, P = 0.032; both compared with TAPSE/PASP <0.34 mm/mmHg). Similar findings were observed for 1-year all-cause mortality.

CONCLUSION

TAPSE/PASP on admission demonstrated a prognostic value among patients with AHF.

Combined pre- and post-capillary pulmonary hypertension in left heart disease

Patients with heart failure (HF) often have pulmonary hypertension (PH), which is mainly post-capillary; however, some of them also develop a pre-capillary component. The exact mechanisms leading to combined pre- and post-capillary PH are not yet clear, but the phenomenon seems to start from a passive transmission of increased pressure from the left heart to the lungs, and then continues with the remodeling of both the alveolar and vascular components through different pathways. More importantly, it is not yet clear which patients are predisposed to develop the disease. These patients have some characteristics similar to those with idiopathic pulmonary arterial hypertension (e.g., young age and frequent incidence in female gender), but they share cardiovascular risk factors with patients with HF (e.g., obesity and diabetes), with both reduced and preserved ejection fraction. Thanks to echocardiography parameters and newly introduced scores, more tools are available to distinguish between idiopathic pulmonary arterial hypertension and combined PH and to guide patients' management. It may be hypothesized to treat patients in whom the pre-capillary component is predominant with specific therapies such as those for idiopathic pulmonary arterial hypertension; however, no adequately powered trials of PH-specific treatment are available in combined PH. Early evidence of clinical benefit has been proven in some trials on phosphodiesterase type 5 inhibitors, while data on prostacyclin analogues, endothelin-1 receptor antagonists, and soluble guanylate cyclase stimulators are still controversial.

Left atrial conduit function: A short review

Three-dimensional echocardiography can elucidate the phasic functions of the left atrium if a simultaneous acquisition of a pyramidal full-volume dataset, as gathered from the apical window and containing the entire left atrial and left ventricular cardiac sections, is obtained. Hence, conduit can be quantified as the integral of net, diastolic, instantaneous difference between synchronized atrial and ventricular volume curves, beginning at minimum ventricular cavity volume and ending just before atrial contraction. Increased conduit can reflect increased downstream suction, as conduit would track the apex-to-base intracavitary pressure gradient existing, in early diastole, within the single chamber formed by the atrium and the ventricle, when the mitral valve is open. Such a gradient increases in response to adrenergic stimulation or during exercise and mediates an increment in passive flow during early diastole, with the ventricle being filled from the atrial reservoir and, simultaneously, from blood drawn from the pulmonary veins. In this context conduit, and even more conduit flow rate, expressed in ml/sec, can be viewed as an indirect marker of left ventricular relaxation. It is well known, however, that a large amount of conduit (in relative terms) is also supposed to contribute to LV stroke volume in conditions of increased resistance to LV filling, when diastolic function significantly worsens. Stiffening of the atrio-ventricular complex implies increments in LA pressure more pronounced in late systole, causing markedly elevated "v" waves, independently of the presence of mitral insufficiency. The combination of increased atrio-ventricular stiffness and conduit flow is associated with an elevation of the right ventricular pulsatile relative to resistive load that negatively impacts on exercise capacity and survival in these patients. Atrial conduit is an "intriguing" parameter that conveys a noninvasive picture of the complex atrioventricular coupling condition in diastole and its backward effects on the right side of the heart and the pulmonary circulation. Given the easiness associated with its correctly performed quantification in the imaging laboratory, I am sure that conduit will survive the competitive access to the list of valuable parameters capable of deciphering, although not necessarily simplifying, the complex diastolic scenario in health and disease.