Effect of beta-blocker therapy on survival in patients with severe aortic regurgitation results from a cohort of 756 patients

Gender Effects on Left Ventricular Responses and Survival in Patients with Severe Aortic Regurgitation: Results from a Cohort of 756 Patients with up to 22 Years of Follow-Up

OBJECTIVES

We sought to evaluate the effect of gender on biology, therapeutic decisions, and survival in patients with severe aortic regurgitation (AR).

BACKGROUND

Gender affects adaptive response to the presence of valvular heart diseases and therapeutic decisions. The impact of these on survival in severe AR patients is not known.

METHODS

This observational study was compiled from our echocardiographic database which was screened (1993-2007) for patients with severe AR. Detailed chart reviews were performed. Mortality data were obtained from the Social Security Death Index and analyzed as a function of gender.

RESULTS

Of the 756 patients with severe AR, 308 (41%) were women. Over a follow-up of up to 22 years, there were 434 deaths. Women compared to men were older (64 ± 18 vs. 59 ± 17 years, p = 0.0002). Women also had smaller left ventricular (LV) end diastolic dimension (5.2 ± 1.1 vs. 6.0 ± 1.0 cm, p < 0.0001), higher EF (56% ± 17% vs. 52% ± 18%, p = 0.003), higher prevalence of diabetes mellitus (18% vs. 11%, p = 0.006), and higher prevalence of ≥2+ mitral regurgitation (52% vs. 40%, p = 0.0008) despite a smaller LV size. Women were also less likely to receive aortic valve replacement (AVR) (24% vs. 48%, p < 0.0001) compared to men and had a lower survival on univariate analysis (p = 0.001). However, after adjusting for group differences including AVR rates, gender was not an independent predictor of survival. However, the survival benefit associated with AVR was similar in both women and men.

CONCLUSIONS

This study strongly suggests that female gender is associated with different biological responses to AR compared to men. There is also a lower AVR rate in women, but women derive similar survival benefit as men with AVR. Gender does not seem to affect survival in an independent fashion in patients with severe AR after adjusting for group differences and AVR rates.

Predictive value of heart rate in patients with acute type A aortic dissection: a retrospective cohort study

OBJECTIVE

Heart rate (HR) is a risk factor of mortality in many cardiovascular diseases but no clinical studies have focused on the association between HR and prognosis in patients with acute type A aortic dissection (ATAAD). This study aimed to evaluate the association between HR and long-term mortality and establish the criteria of HR in patients with ATAAD who underwent total aortic arch replacement combined with the frozen elephant trunk (TAR+FET).

DESIGN, SETTING AND PARTICIPANTS

Retrospective cohort study that studied all consecutive patients with ATAAD who underwent TAR+FET in the Fuwai Hospital between 2009 and 2015.

MAIN OUTCOMES AND MEASURES

30-day postoperative, and estimated long-term mortality.

RESULTS

Overall, 707 patients with ATAAD who underwent TAR+FET were followed up for a median duration of 29 months (range, 5-77 months). In multivariate logistic analysis, HR (p<0.001), age (p<0.001), renal insufficiency (p=0.033), ejection fraction (p=0.005), cardiopulmonary bypass time (p<0.001) and intraoperative blood loss (p=0.002) were significantly associated with 30-day postoperative and estimated long-term mortalities. A hinge point with a sharp increase in estimated long-term mortality was identified at 80 beats/min (bpm), and compared with HR ≤80 bpm, HR >80 bpm was associated with an almost threefold higher long-term mortality. HRs ≤60, 60-70, 70-80, 80-90, 90-100, 100-110 and >110 bpm were associated with 3.9%, 4.0%, 3.8%, 7.2%, 9.5%, 10.1% and 14.4% yearly risks of death, respectively.

CONCLUSIONS

HR is a powerful predictor of long-term mortality in patients with ATAAD undergoing TAR+FET. HR >80 bpm is independently associated with elevated long-term mortality for patients with ATAAD.

Medical Therapies for Marfan Syndrome and Other Thoracic Aortic Dilatation in Adults: A Contemporary Review

Thoracic aortic dilatation often has an asymptomatic course but may present with lethal complications such as aortic rupture or dissection, particularly when the thoracic aorta is aneurysmally enlarged; therefore, appropriate diagnosis, surveillance, and management are vital. Recommendations regarding imaging and surgical management are outlined in contemporary clinical practice guidelines. Dedicated guidelines regarding medical therapies for the management of thoracic aortic dilatation are lacking. Most of the medical treatment strategies, especially recommendations regarding pharmacological medical therapies related to β-blockade and angiotensin receptor blockers, are derived from data on patients with Marfan syndrome. The main aims of medical therapies for the management of thoracic aortic dilatation are (1) to control the progression of the disease, and (2) to prevent complications related to the disease (such as aortic dissection and mortality). This paper reviews the contemporary evidence and highlights the gaps in evidence to be investigated in further studies.

Optimal Management of Chronic Severe Aortic Regurgitation - How to Determine Cutoff Values for Surgical Intervention?

Aortic regurgitation (AR) is a common valvular heart disease, but the optimal timing of surgical intervention remains controversial. In the natural history of chronic severe AR, sudden death is rare, and the annual mortality rate is comparatively low. Considering the hemodynamic features of combined volume and pressure overload and long-term compensation in patients with chronic AR, symptoms related to AR do not frequently occur. Therefore, the progression of left ventricular (LV) dysfunction is a key factor in determining the timing of surgical intervention in patients with severe chronic AR. In addition to symptoms, an ejection fraction <50% and an LV endsystolic diameter (LVESD) >45 mm are appropriate cutoff values for surgical intervention in Japanese patients, whereas LV end-diastolic diameter is not a good indicator. An LVESD index of 25 mm/m²is controversial, because adjusting for body size may cause overcorrection in Japanese patients who have a small body size compared with Westerners. Accumulation of data from the Japanese population is indispensable for establishing guidelines on optimal management of patients with chronic AR.

Adverse Outcomes with Eccentric Hypertrophy in a Community Based University Cohort with Aortic Stenosis

OBJECTIVE

Aortic stenosis (AS) patients with eccentric hypertrophy (Ecc-LVH) have increased left ventricular (LV) size and possibly reduced ejection fraction (EF). However, previous studies suggest worse outcomes with concentric remodeling and hypertrophy. We hypothesized that Ecc-LVH pattern in AS patients will also be associated with greater heart failure (HF) and all-cause mortality (ACM).

METHODS

We queried the electronic medical record from a community-based university practice for all AS patients. We included patients with >60 days follow-up and interpretable Doppler echocardiograms. We recorded demographics, Doppler-echo parameters, laboratories, HF readmission and ACM with follow-up to 2083 days. There were 329 patients divided into 4 groups based on the presence of LV hypertrophy (LVH) and relative wall thickness (RWT) by echocardiography. Ecc-LVH had RWT<0.43 and LVH.

RESULTS

Patients with severe AS were older, had greater coronary disease prevalence, lower hemoglobin, greater LV mass index, more abnormal diastolic function, greater HF and ACM. Multivariate Cox proportional analysis revealed that valvulo-arterial impedance (p=0.017) and Ecc-LVH (p=0.033) were HF predictors. Brain natriuretic peptide>100 pg/ml (p<0.001) and Ecc-LVH (p=0.019) were ACM predictors. ACM was increased in Ecc-LVH patients with both moderate (HR=3.67-8.18 vs other geometries, p=0.007-0.0007) and severe AS (HR=3.94-9.48 vs normal and concentric remodeling, p=0.0002). In patients with HF, Ecc-LVH was associated with greater HF in moderate AS vs normal geometry (HR=3.28, p=0.0135) and concentric remodeling (HR=2.66, p=0.0472).

CONCLUSIONS

Patients with AS and Ecc-LVH have greater ACM than other LV geometries with both moderate and severe AS and greater HF in moderate AS.

Therapeutic Controversies in the Medical Management of Valvular Heart Disease

Objective:

To evaluate the evidence for common therapeutic controversies in the medical management of valvular heart disease (VHD).

Data Sources:

A literature search of PubMed (inception to December 2020) was performed using the terms angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) and aortic stenosis (AS); and adrenergic β-antagonists and aortic valve regurgitation (AR) or mitral stenosis (MS).

Study Selection and Data Extraction:

Randomized controlled trials (RCTs) and meta-analyses conducted in humans and published in English that reported ≥1 clinical outcome were included.

Data Synthesis:

Nine articles were included: 3 RCTs and 1 meta-analysis for ACE inhibitors/ARBs in AS, 1 RCT for β-blockers in AR, and 4 RCTs for β-blockers in MS. Evidence suggests that ACE inhibitors/ARBs do not increase the risk of adverse outcomes in patients with AS but may delay valve replacement. β-Blockers do not appear to worsen outcomes in patients with chronic AR and may improve left-ventricular function in patients with a reduced ejection fraction. β-Blockers do not improve and may actually worsen exercise tolerance in patients with MS in sinus rhythm.

Relevance to Patient Care and Clinical Practice:

ACE inhibitors/ARBs and β-blockers can likely be safely used in patients with AS or AR, respectively, who have a compelling indication. There is insufficient evidence to recommend routine use of β-blockers in patients with MS without atrial fibrillation.

Conclusions:

Common beliefs about the medical treatment of VHD are not supported by high-quality data. There remains a need for larger-scale RCTs in the medical management of VHD.

The advantages, pitfalls and limitations of guideline-directed medical therapy in patients with valvular heart disease

Heart failure is an inevitable end-stage consequence of significant valvular heart disease (VHD) that is left untreated and increasingly encountered in an ageing society. Recent advances in transcatheter procedures and improved outcomes after valve surgery mean that intervention can (and should) be considered in all patients - even the elderly and those with multiple comorbidities - at earlier stages of the natural history of primary VHD, before the onset of irreversible left ventricular dysfunction (and frequently before the onset of symptoms). All patients with known VHD should be monitored carefully in the setting of a heart valve clinic and those who meet guideline criteria for surgical or transcatheter intervention referred for intervention without delay. High quality evidence for the use of medical therapy in VHD is limited and achieving target doses in an elderly and comorbid population frequently challenging. Furthermore, determining whether the valve or ventricle is the principal disease driver is crucial (although the distinction is not always binary, and often unclear). Guideline-directed medical therapy remains the mainstay of treatment for secondary mitral regurgitation - although up to 50% of patients may fail to respond and should be considered for cardiac resynchronization, transcatheter or surgical valve intervention. Early and definitive management strategies are essential and should be overseen by a specialist Heart Team that includes a Heart Failure specialist. In this article, we provide an evidence-based summary of approaches to the medical treatment of VHD and clinical guidance for the best management of patients in situations where high quality evidence is lacking.

Current trends in aortic valve-preserving surgery

The natural history of aortic regurgitation is not as benign as once believed, even in asymptomatic patients with preserved left ventricular function. Aortic valve surgery can prolong survival in these patients. However, both mechanical and biological aortic valve replacement have major disadvantages, especially in young patients. Aortic valve-preserving surgery has attracted a great deal of attention because it has a significant survival benefit over replacement. Nonetheless, aortic valve-preserving surgery has not been widely adopted due to the complexity of the technique and assessment (i.e., long learning curve). With recent technical and theoretical advances, aortic valve-preserving surgery has increasingly been performed with better outcomes, and therefore earlier surgical intervention in cases of aortic regurgitation has been considered. Recent advances in aortic valve-preserving surgery include repair-oriented classification of the etiology of aortic regurgitation, objective assessment of the cusp configuration (i.e., effective height and geometric height), use of aortic annuloplasty, introduction of two reproducible valve-sparing root replacement procedures (i.e., aortic valve reimplantation and aortic root remodeling techniques), standardization of aortic valve-preserving surgery, and assessment of cusp configuration with aortoscopy. A number of prospective multicenter studies are currently underway and will clarify the role of aortic valve-preserving surgery in the treatment of aortic regurgitation in the near future.

Aortic Stenosis, Aortic Regurgitation and Arterial Hypertension

BACKGROUND

Hypertension (HT) is an important risk factor for cardiovascular disease and might precipitate pathology of the aortic valve.

OBJECTIVE

To investigate the association of HT with aortic dysfunction (including both aortic regurgitation and stenosis) and the impact of antihypertensive treatment on the natural course of underlying aortic disease.

METHODS

We performed a systematic review of the literature for all relevant articles assessing the correlation between HT and phenotype of aortic disease.

RESULTS

Co-existence of HT with aortic stenosis and aortic regurgitation is highly prevalent in hypertensive patients and predicts a worse prognosis. Certain antihypertensive agents may improve haemodynamic parameters (aortic jet velocity, aortic regurgitation volume) and remodeling of the left ventricle, but there is no strong evidence of benefit regarding clinical outcomes. Renin-angiotensin system inhibitors, among other vasodilators, are well-tolerated in aortic stenosis.

CONCLUSION

Several lines of evidence support a detrimental association between HT and aortic valve disease. Therefore, HT should be promptly treated in aortic valvulopathy. Despite conventional wisdom, specific vasodilators can be used with caution in aortic stenosis.

Comparison of effects of losartan and metoprolol on left ventricular and aortic function at rest and during exercise in chronic aortic regurgitation

Aortic regurgitation (AR) increases the hemodynamic load on both the left ventricle (LV) and the aorta. Vasodilators and beta-blockers both reduce systemic blood pressure, but their relative effects on the LV and aortic function and aortic regurgitant fraction in chronic AR are uncertain. We aimed to compare short-term effects of losartan and metoprolol on LV and aortic function in asymptomatic patients with chronic moderate to severe AR, both at rest and during exercise, using cardiac magnetic resonance (CMR) imaging. 17 chronic AR patients were randomized to 4-6 weeks losartan followed by metoprolol, or vice versa, in a cross-over design. Aortic regurgitant fraction, aortic distensibility, pulse wave velocity and LV function were assessed at rest and after moderate exercise stress (29 ± 7 W, heart rate increase 25 ± 6 bpm) using CMR. Chronic AR patients on metoprolol had a significantly lower mean heart rate, cardiac power index and rate-pressure product, than on losartan (all p < 0.01). However, aortic regurgitant fraction was greater on metoprolol compared to losartan (by 7 ± 11%, p = 0.02). Metoprolol was also associated with a greater reduction in aortic distensibility during exercise than losartan (- 2.4 ± 1.5 × 10^-3 vs - 1.7 ± 2.1 × 10^-3 mmHg^-1 respectively, p = 0.04). End-diastolic volume index was higher on metoprolol than losartan at exercise (difference 6.6 ± 7.8 ml/m², p < 0.01), as was end-systolic volume index (difference 4.0 ± 5.2 ml/m², p < 0.01). Losartan and metoprolol have significantly different short-term effects on aortic regurgitation and LV and aortic function in chronic AR. Further research is required to determine the long-term clinical significance of these changes.

[Management of multiple valve disease]

Polyvalvular disease is not a rare condition, the lack of specific data for each situation does not allow perfoming standardized management and guidelines. We want to present by this review available data on the management of polyvalvular disease, taking into account different possible associations between the valve lesions.

Current Management of Patients with Severe Aortic Regurgitation

OPINION STATEMENT

Chronic aortic regurgitation can result from various congenital and acquired anomalies and can be associated with proximal aortic disease. As the number of aortic valve procedures is growing, the incidence of post-procedural regurgitation also increases with associated morbidity. Typical evolution is characterized by a clinically silent phase of variable duration followed by a rather rapid decline with high incidence of adverse events. A challenge remains to find the optimal timing for an intervention: Patients are exposed to unnecessary surgical risks if treated prematurely, but peri- and post-operative prognosis is worse when the intervention is performed too late. Clinical evaluation and serial imaging tests can optimize the timing for intervention. Clinical follow-up should try to elucidate associated symptoms, with quantitative measurement of functional capacity as needed. Serial imaging examinations are required to identify sub-clinical left ventricular dysfunction or severe dilatation that should prompt a surgery. At least in selected cases, newer imaging modalities (MRI, 3D echocardiography) and/or biomarkers can help for the management of these patients, and more research is needed to determine if their systematic use can be beneficial. Medical treatment with vasodilators and anti-remodeling drugs can be helpful in some patients but should not replace or delay aortic valve surgery when indicated. Most patients will eventually be treated with surgical aortic valve replacement. Although possible in selected cases, transcatheter aortic valve replacement is not commonly used for patients with pure aortic regurgitation. For patients with prior aortic valve replacement and aortic regurgitation (paravalvular or intravalvular), emerging percutaneous approaches can be considered when available, especially for those at high surgical risk.

How to follow patients with mitral and aortic valve disease

Valvular heart diseases (VHDs) place a hemodynamic load on the left and/or right ventricle that, if severe, prolonged, and untreated, damages the myocardium, leading to heart failure and death. Because all VHDs are mechanical problems, definitive therapy usually requires valve repair or replacement. In most valve disease the onset of symptoms marks a change in disease prognosis and is usually an indication for prompt surgical correction. Echocardiography is an indispensable modality for assessing lesion severity, its effect on cardiac function, and the proper timing for lesion correction. Intervention enhanced with percutaneous options now allows patients to benefit from mechanical correction.

Characterization of coronary flow reserve and left ventricular remodeling in a mouse model of chronic aortic regurgitation with carvedilol intervention

OBJECTIVES

We hypothesized that left ventricular (LV) remodeling might be exaggerated by an impaired coronary flow reserve in mice with chronic severe aortic regurgitation, and carvedilol, a β-adrenoceptor blocker, could regress the course.

METHODS

Severe aortic regurgitation was induced by retrograde puncture of the aortic valve leaflets under sonographic guidance in 12-week-old male C57BL/6J mice. Four weeks after regurgitation, the mice were treated with carvedilol (30 mg/kg/d) or not treated (control). Before and 4 weeks after carvedilol treatment, the coronary flow reserve and LV structure and function were evaluated by echocardiography. Cardiomyocytes and fibrosis were validated by histologic analysis.

RESULTS

Four-week aortic regurgitation caused a decreased LV ejection fraction and an increased LV end-systolic volume index. Regurgitation also impaired the coronary flow reserve due to an increase in the basal coronary peak diastolic velocity and velocity-time integral combined with the absence of substantial changes in the hyperemic coronary peak diastolic velocity and velocity-time integral. Four more weeks of regurgitation further deteriorated LV remodeling and coronary perfusion in the control group. In contrast, the carvedilol-treated group showed attenuated LV remodeling and a higher coronary flow reserve by decreasing the basal peak diastolic velocity and velocity-time integral without substantial changes in the hyperemic peak diastolic velocity and velocity-time integral. The coronary flow reserve and its pretreatment versus posttreatment difference were positively correlated with the pretreatment versus posttreatment LV ejection fraction and end-systolic volume index differences. In the carvedilol-treated group, subendocardial fibrosis was significantly reduced (P < .05), and the cardiomyocyte cross-sectional area tended to be smaller.

CONCLUSIONS

In mice with chronic severe aortic regurgitation, carvedilol therapy significantly improves the impaired coronary flow reserve and sufficiently attenuates adverse LV remodeling. Sustained coronary flow reserve impairment indicates progressive LV remodeling.

Effects of early and late-onset treatment with carvedilol in an experimental model of aortic regurgitation

Background

Beta-blockade is contraindicated in severe aortic regurgitation (AR) due to the fear of prolonging diastole and thus aggravate regurgitation. However, this has never been scientifically proven and positive effects of targeting the sympathetic system in AR has been demonstrated in several studies.

Method

Thirty-nine Sprague–Dawley rats with AR were randomized to ten weeks of medical treatment with carvedilol or no treatment. Treatment was initiated either early or late after AR induction. The effect of carvedilol was assessed by serial echocardiography and invasive hemodynamic measurements.

Results

AR resulted in eccentric hypertrophy and left ventricular (LV) dysfunction. LV remodeling and function as measured by echocardiography was unaffected by treatment. LV dimensions were similar between treated and untreated groups and measures of LV performance (including strain and strain rate) were also unaltered. This result was confirmed by invasive measurements showing maximal and minimal pressure–time development, LV volumes, and LV pressures, to be unaltered by treatment. On the contrary, despite relative bradycardia carvedilol did not reflect any negative impact on the heart.

Conclusion

Carvedilol did not improve left ventricular remodeling or function in rats with surgically induced AR. Despite relative bradycardia, we did not find carvedilol to negatively impact the heart, either when treatment was initiated early or late in the course of disease.

Prognostic value of cardiac magnetic resonance imaging in patients with aortic regurgitation

Guidelines on valve replacement recommend aortic valve replacement for patients with severe aortic regurgitation (AR) with symptoms or left ventricular (LV) dysfunction. However, the optimal timing of surgery for asymptomatic AR patients without LV dilation or dysfunction is not known. There are data to suggest that excess volume load imposed by AR may not only produce subclinical LV dysfunction, but produce neurohormonal activation similar to the heart failure syndrome resulting in reduced survival. The study by Myerson et al. is the first to investigate the predictive ability of cardiac MRI (CMR) for the outcome of asymptomatic patients with AR. They studied 113 asymptomatic patients with moderate-to-severe AR on echocardiography in four centers. A total of 39 (35%) patients developed symptoms or an indication for surgery over a mean follow-up period of 2.6 years. AR volume, AR regurgitant fraction, LV end-diastolic and end-systolic volumes had high discriminatory powers (area under curve of 0.96, 0.93, 0.88 and 0.78, respectively) to predict these events. Higher association with the outcome was observed when LV end-diastolic volume and regurgitant fraction were combined. A significantly higher number of patients with regurgitant fraction >33% were likely to progress to surgery compared with patients with a regurgitant fraction of <33% (85 vs 8%; p < 0.001). These results demonstrate a potential role for CMR for risk stratification of patients with asymptomatic moderate or severe AR, given the ability of CMR to accurately quantify AR and LV volumes. Based on the data presented, it is possible that we may be waiting too long to offer surgery in patients with severe AR.

Usefulness of Carvedilol in the Treatment of Chronic Aortic Valve Regurgitation

Background—

Aortic regurgitation (AR) is a chronic disease for which there is currently no approved medical treatment. We previously reported in an animal model that β-blockade with metoprolol exerted beneficial effects on left ventricular remodeling and survival. Despite the recent publication of promising human data, β-blockade in chronic AR remains controversial. More data are needed to support this potentially new treatment strategy. We hypothesized that carvedilol might be another safe treatment option in chronic AR, considering its combined β-blocking and α-blocking effects and proven efficacy in patients with established heart failure.

Methods and Results—

The effects of a 6-month treatment with carvedilol 30 mg/kg/d orally were evaluated in adult Wistar rats with severe AR. Sham-operated and untreated AR animals were used as controls. Carvedilol treatment resulted in less left ventricular hypertrophy and dilatation. Ejection fraction was improved and filling pressures were reduced by carvedilol. β1-Receptor expression was also improved as well as myocardial capillary density. Those beneficial effects were noted despite the presence of drug-induced bradycardia.

Conclusions—

Carvedilol exerted protective effects against volume-overload cardiomyopathy in this model of aortic valve regurgitation with preserved ejection fraction. These results suggest a protective class effect of β-blockers. Combined with the recent publication of promising human data, our findings support the need to carefully design a prospective study in humans to evaluate the effects of β-blockers in chronic aortic valve regurgitation.

Prognostic implications of mitral regurgitation in patients with severe aortic regurgitation

BACKGROUND

Mitral regurgitation (MR) is common in those with severe aortic regurgitation (AR) and can predispose to atrial fibrillation, heart failure, and a need for mitral valve surgery during aortic valve replacement (AVR). However, little data exist as to its clinical and prognostic implications.

METHODS AND RESULTS

Search of our echocardiographic data base between 1993 and 2007 yielded 756 patients with severe AR. with comprehensive clinical data from chart review and mortality data from National Death Index. Mortality was analyzed as a function of MR severity. Effect of AVR and concomitant mitral valve repair were investigated. Patient characteristics were age, 61±17 years; female sex, 41%; and ejection fraction, 54±19%. MR grade ≥2+ was present in 343 (45%) patients: 2+ in 152 (20%), 3+ in 93 (12%), and 4+ in 98 (13%). There was a progressive decrease in survival with each grade of MR (P<0.0001). Performance of AVR was associated with a better survival in those with 3 or 4+ MR (P=0.02). In addition, concomitant mitral valve repair in these patients resulted in a better survival (hazard ratio, 0.29; P=0.02).

CONCLUSIONS

MR is common in patients with severe AR, with 3 or 4+ MR occurring in a quarter of these patients. It is an independent predictor of reduced survival. Performance of AVR and concomitant mitral valve repair is associated with a better survival. Development of MR should serve as an indication for AVR even in asymptomatic patients.

Survival benefit of aortic valve replacement in patients with severe aortic regurgitation and pulmonary hypertension

BACKGROUND

Severe pulmonary hypertension occurs in approximately 10% of patients with severe aortic regurgitation (AR). The potential survival benefit of aortic valve replacement (AVR) in these patients is not known, and was analyzed in a large cohort of patients.

METHODS

Our echocardiographic data was screened for severe AR patients with severe pulmonary hypertension defined as pulmonary artery systolic pressure of 60 mm Hg or greater. Chart reviews were performed for clinical, pharmacologic, and surgical details, and survival data were analyzed as a function of AVR.

RESULTS

Of the 506 patients with severe AR and measurable pulmonary artery pressures by echocardiography, 83 had severe pulmonary hypertension defined as a pulmonary artery systolic pressure of 60 mm Hg or greater. Severe pulmonary hypertension was associated with lower left ventricular ejection fraction (47% +/- 22% versus 53% +/- 19%, p = 0.006), larger left ventricular size (p = 0.03), and higher grades of mitral regurgitation (2.7 +/- 1.2 versus 1.7 +/- 1.1, p < 0.0001). Of the 83 patients with severe pulmonary hypertension, 32 underwent AVR, which was associated with better survival compared with patients who did not (1-year survival 90% versus 58% and 5-year survival 62% versus 22%, respectively; p = 0.004). After adjusting for comorbidities, AVR remained an independent predictor of better survival (hazard ratio 0.45, 95% confidence interval: 0.22 to 0.92, p = 0.03). This survival benefit of AVR was further supported by propensity score analysis.

CONCLUSIONS

Severe pulmonary hypertension occurs in approximately 16% of patients with severe AR and is associated with left ventricular enlargement with dysfunction and resultant mitral regurgitation. Aortic valve replacement is associated with an independent survival benefit in these patients.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.