Magnitude of left atrial V wave is the determinant of exercise capacity in patients with mitral stenosis

Hemodynamic function of the right ventricular-pulmonary vascular-left atrial unit: normal responses to exercise in healthy adults

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise.

Left atrial compression and right ventricular outflow tract diameter on echocardiography are independently associated with exercise capacity in patients with large hiatal hernia

INTRODUCTION

Large hiatal hernia (HH) is often associated with left atrial (LA) compression, anteroposterior cardiac compression (manifesting as reduced right ventricular outflow tract (RVOT) diameter), and left ventricular (LV) compression (manifesting as systolic paradoxical outward motion (LV-PM) of the posterobasal LV segment). Exercise impairment, also common in this population, improves following HH surgery. We aimed to identify echocardiographic parameters independently associated with exercise impairment due to HH-mediated cardiogenic compression.

METHODS

Patients with a large HH (>30% intra-thoracic stomach, n = 163) referred for cardiac evaluation were included. Echocardiographic parameters were retrospectively analyzed in relation to HH-related LA compression severity and the presence of LV-PM. Echocardiographic parameters independently associated with exercise capacity were identified by multivariable analysis.

RESULTS

Mean baseline metabolic equivalents were reduced (70 ± 28% predicted). Moderate-severe LA compression and LV-PM were present in 91 of 163 (56%) and 65 of 162 (40%) patients, respectively. Patients with moderate-severe LA compression and LV-PM had decreased LA and LV dimensions. Moderate-severe LA compression was also associated with reduced RVOT diameter while LV-PM predicted a greater reduction in LV volumes. LA compression and RVOT diameter were independently associated with baseline exercise capacity and increased following HH surgery performed in a subgroup (n = 72, LA diameter: 14 ± 5 vs 20 ± 4 mm/m² ; RVOT diameter: 17 ± 3 vs 19 ± 3 mm/m² , P < .001 for both). Conversely, LV-PM was not independently associated with exercise capacity.

CONCLUSION

Hiatal hernia-related cardiac compression reduces LA and RVOT dimensions. These parameters are independently associated with baseline exercise capacity and improve following HH surgery. LV-PM is associated with decreased LV volumes but not exercise capacity in this population.

Update on drug-eluting coronary stents

The introduction of drug-eluting stents (DES) to interventional cardiology practice has resulted in a significant improvement in the long-term efficacy of percutaneous coronary interventions. DES successfully combine mechanical benefits of bare-metal stents and stabilizing the lumen, with direct delivery and the controlled elution of a pharmacologic agent to the injured vessel wall to suppress further neointimal proliferation. The dramatic reduction in restenosis has resulted in the implementation of DES in clinical practice, and has rapidly expanded the whole spectrum of successfully treatable coronary conditions, particularly in high-risk patients and complex lesions. In this review the authors present current data on DES. Currently, two types of DES are available in the USA: sirolimus-eluting stents (SES) CYPHER (Cordis Corp., FL, USA) and paclitaxel-eluting stents (PES) TAXUS (Boston Scientific, MA, USA), and many more are on the way to approval. In addition to sirolimus and paclitaxel, several other drugs have been successfully used in DES. Everolimus and ABT-578 are both analogs of sirolimus that also have immunosuppressive and antiproliferative properties. Another approach in the development of DES is to use drugs that can accelerate re-endothelialization and restore normal endothelial function following vascular injury. Recent advances in vascular gene transfer have also demonstrated potential new treatment modalities for cardiovascular disease, particularly in the treatment of vascular restenosis.

Atrial dyssynchrony syndrome: an overlooked phenomenon and a potential cause of 'diastolic' heart failure

AIMS

The purpose of the present study was too explore the role of interatrial dyssynchrony in heart failure with preserved ejection fraction (HFPEF).

METHODS AND RESULTS

For the case study we selected seven patients with severe HFPEF, with interatrial block on electrocardiogram (ECG), and a delayed and interrupted A wave on mitral Doppler. Echocardiographic left atrial (LA) volumes/functions, mitral E/A and E/e' ratios, mitral A wave duration/deceleration time, and interatrial mechanical delays (IAMDs) at tissue Doppler, were studied. We performed right heart catheterization, and an electrophysiological study (EPS) for the measurement of interatrial conduction delay (IACD) and left atrioventricular interval (LAVI). Mean IAMD was 106 ms. All the patients exhibited a restrictive mitral Doppler pattern, high E/A and E/e' ratios, and short A wave duration/deceleration time. Left atrial volume was increased, with severely depressed functions. Right heart catheterization showed severe post-capillary pulmonary hypertension. The EPS showed an IACD of 170 ± 20 ms, with a short LAVI. Left atrial pacing through the coronary sinus reduced the IACD to 25 ± 15 ms. In the pilot study, 29 patients with HFPEF were compared with 27 age-matched control patients. HFPEF patients had longer P waves, shorter A waves, and a longer IAMD than the controls. Prevalence of severe IAMD >60 ms was 59% in HFPEF and 0% in controls. In the HFPEF group, patients with an IAMD >60 ms had significantly shorter A waves and higher E/e' ratio.

CONCLUSION

Some HFPEF patients present with IACD, delayed LA systole, shortened LA emptying, decreased LA compliance, and increased filling pressures. Whether the condition of these patients could be improved by atrial resynchronization deserves further investigation.

Mitral stenosis

Mitral stenosis is a common disease that causes substantial morbidity worldwide. The disease is most prevalent in developing countries, but is increasingly being identified in an atypical form in developed countries. All treatments that increase valve area improve morbidity. Mortality improves with surgery; the benefit of percutaneous balloon valvuloplasty to mortality might be similar to that of surgery but needs further study. Percutaneous balloon valvuloplasty is the treatment of choice for patients in whom treatment is indicated, except for those with suboptimum valve morphology, and even these patients are sometimes treated with this procedure if surgery is not feasible or if surgical risk is prohibitive. We review the pathology, diagnosis, and treatment options for patients with mitral stenosis.