Low-gradient aortic stenosis: impact of prosthesis-patient mismatch on survival

AIMS

To assess the prognostic impact of prosthesis-patient mismatch (PPM) in a large consecutive series of patients operated for low-gradient aortic stenosis (AS).

METHODS AND RESULTS

Outcomes after surgery for low-gradient AS were prospectively assessed in 152 consecutive patients from seven institutions. There were 113 men (74%); mean age was 72 years (64-76); valve area, 0.7 cm(2) (0.6-0.8); left ventricular (LV) ejection fraction 0.31 (0.25-0.37) and baseline mean transaortic pressure gradient (MPG), 30 mmHg (25-35) Among 139 patients with available prosthetic valve effective orifice area (EOA), PPM (defined by an indexed EOA < or = 0.85 cm(2)/m(2)) was present in 79 patients (57%) and had no significant impact on post-operative mortality. Independent predictors of overall mortality were LV contractile reserve [hazard ratio (HR) 0.52; 95% confidence interval (CI) 0.35-0.78; P = 0.002], associated coronary artery bypass grafting (HR 1.87; 95% CI 1.24-2.82; P =0.003), baseline MPG (per 1 mmHg decrease to 10 mmHg; HR 1.03; 95% CI 1.01-1.06; P = 0.021), previous cancer (HR 2.13; 95% CI 1.05-4.29; P = 0.037), and logistic EuroSCORE (per 1% increase; HR 1.02; 95% CI 1.01-1.04; P = 0.040). CONCLUSION In this large multicentre series of patients with low-gradient AS, we found that PPM (moderate in most cases) had no influence on post-operative mortality. Therefore, the performance of more complex interventions in order to avoid moderate PPM may not be justified in the setting of low-gradient AS, because their higher risk probably outweighs the expected benefit.

Numerical response of a helminth community in the course of a multi-annual abundance cycle of the Water Vole (Arvicola terrestris)

The impact of parasitism on population dynamics is determined in part by the numerical responses of parasites during population fluctuations of their hosts. Vole populations fluctuate in multi-annual cycles allowing such responses to be studied over successive phases of population growth, abundance and decline. We investigate how a helminth community (5 nematode and 7 cestode species) evolved over a full 6-year Water Vole (Arvicola terrestris) population cycle. Brillouin and individual parasite species richness (IPSR) indices were used to measure the numerical response of the parasite community. We report a correlation between levels of parasite intensity and vole population cycle phases. Both indices were consistently higher during pre-decline and decline phases for male and female voles alike. The numerical response of the parasite community suggests that populations may be regulated by parasitism and that studies of this mechanism should allow both for the cyclic or non-cyclic character of the host populations and for the response of the broadest possible set of the local parasite community.

Influence of Preoperative Left Ventricular Contractile Reserve on Postoperative Ejection Fraction in Low-Gradient Aortic Stenosis

Background— Dobutamine stress hemodynamics (DSH) has the potential to stratify operative risk in low-gradient aortic stenosis (AS), but little is known about the relation between left ventricle contractile reserve and postoperative left ventricular ejection fraction (LVEF). We sought to assess the value of DSH to predict postoperative improvement in LVEF.

Methods and Results— Sixty-six consecutive patients with symptomatic severe AS (aortic valve area ≤1 cm 2 ), LVEF ≤40%, and mean pressure gradient ≤40 mm Hg prospectively enrolled in the French multicenter study on low-gradient AS and who survived to aortic valvular replacement (AVR) were included. Preoperative contractile reserve was present in 46 patients (group I; 70%) and absent in 20 patients (group II; 30%). In the overall sample, 58% of patients improved by 2 New York Heart Association (NYHA) classes after AVR. Mean LVEF improved from 29±6% to 47±11% ( P <0.0001). LVEF improved by ≥10 EF units in 38 patients (83%) in group I and in 13 patients (65%) in group II. Mean LVEF improvement was similar in the 2 groups (19±10% versus 17±11%; P =0.54). On multivariable analysis, multivessel coronary artery disease ( P =0.05) and baseline mean transaortic pressure gradient ( P =0.01) were related to LVEF improvement, whereas contractile reserve was not.

Conclusions— LVEF increases in the majority of patients with low-gradient AS who survive after AVR. Although the absence of contractile reserve on DSH is related to high operative mortality, it does not predict the absence of LVEF recovery in patients surviving to AVR. These data further support the concept that surgery should not be contraindicated on the basis of absence of contractile reserve alone.

An epidemiological and ecological study of human alveolar echinococcosis transmission in south Gansu, China

Human alveolar echinococcosis (AE) is usually a rare, highly pathogenic zoonotic disease, transmitted across the northern hemisphere between fox and rodent hosts. In China the first cases were described in 1965; however very few epidemiological studies have been undertaken since. Following identification in 1991 of a serious focus of human AE in south Gansu province, detailed village-based community and ecological studies were carried out between 1994 and 1997. Hepatic ultrasound mass screening with serological testing (five tests) identified 84/2482 new AE cases (3%). An overall prevalence of 4.1% (135/3331) was recorded for the area when previous cases were also included. Based on a seropositive result only, without an ultrasound scan indication, no additional AE cases were identified. Of the evolutive AE cases, 96% were seropositive in at least one test, while up 15-20% of individuals who exhibited hepatic calcified lesions and 12-15% exhibiting hepatic nodular lesions were seropositive for specific Em2 or Em18 antibodies. Village (n=31) human AE prevalence rates varied from 0 to 15.8%. Questionnaire analysis indicated that total number of dogs owned over a period was a risk factor (P<0.006), but not a history of red fox hunting (P>0.6). Rodent ecology studies revealed an association between density indices of voles (Microtus limnophilus) and village AE prevalence rates, on the one hand, and village landscape characterised by a ratio of scrub/grassland to total area above 50% (P<0.005). Long-term transmission of Echinococcus multilocularis and risk of zoonotic infection of south Gansu farmers may be related ultimately to a process of deforestation driven by agriculture. This in turn probably results in creation of optimal peri-domestic habitats for rodents that serve as intermediate host species (such as M. limnophilus) and subsequent development of a peri-domestic cycle involving dogs.

[Malignant cardiac lymphoma. Diagnosis by echocardiography]

The authors report a case of cardiac malignant non-Hodgkin lymphoma. The initial clinical presentation suggested recurrent angina in a patient who had undergone angioplasty of the left anterior descending artery two years previously. Echocardiography showed severe left ventricular dysfunction with apical and septal akinesia and also allowed visualisation of two oval masses in the right ventricle without dilatation of the right heart chambers. Transoesophageal echocardiography confirmed these abnormal echos which corresponded to tumour invasion of not only the right heart chambers but also the interatrial septum, the left atrial appendage and the descending thoracic aorta. Histological diagnosis of lymphoma was made from an excision biopsy of a mass in the calf muscle. The post-mortem examination confirmed the presence of a highly malignant T-cell non-Hodgkin lymphoma. The patient rapidly deteriorated and died during the first session of chemotherapy.

[Recording of pulmonary venous flow with Doppler echocardiography; normal and pathological aspects]

The appearances of pulmonary venous flow Doppler echocardiography have been the subject of many reports. The recording is obtained by transthoracic or transoesophageal pulsed Doppler examination. The value of this parameter in the study of left ventricular diastolic function has been clearly established. The transoesophageal approach is mainly useful for quantifying mitral regurgitation and for monitoring left atrial pressure during surgery. This review of the literature describes the methods of recording and the normal appearances of pulmonary venous flow, and then discusses the different variations encountered in pathological conditions.

[Quantification of mitral valve diseases by Doppler]

Echo Doppler makes a fundamental contribution to the non-invasive quantification of mitral valve disease. It enables calculation of gradients and of orifice surface area in mitral stenosis. The quantification of mitral insufficiency is also possible though more difficult: it is based upon the combination of semi-quantitative and quantitative methods, in particular the calculation of regurgitation fraction obtained by comparison of flow rates at different orifices in cases of pure regurgitation. Finally, the calculation of pulmonary artery pressures from a Doppler record in tricuspid and pulmonary insufficiency can be used to assess the effects of mitral valve disease on the pulmonary circulation. Echo Doppler thus provides a reliable non-invasive hemodynamic assessment of mitral valve disease and should lead to a reduction in the number of invasive investigations in this type of valve disease.

[Determination of cardiac output by Doppler ultrasonics. Principle, techniques and limitations]

The development of quantitative applications of Doppler ultrasound for the measurement of cardiac output was a lengthy and difficult process. These applications call for rigor of the part of the ultrasound cardiographer and a sufficiently echoic patient. Numerous studies have demonstrated the reliability of Doppler ultrasound in determining aortic flow. A high degree of consensus has emerged for measuring aortic areas and velocities at the ring. Doppler ultrasound quantification of the pulmonary flow has been validated in children. In adults, measurement of the pulmonary ring is often difficult and may lead to major errors in the estimation of the flow rates. The determination of mitral flow is also possible, either at the ring or at the tip of the mitral funnel. A few publications highlight the value of Doppler ultrasound in evaluation of tricuspid flow, however, these results require confirmation.