Influence of valve prosthesis type on the recovery of ventricular dysfunction and subendocardial ischaemia following valve replacement for aortic stenosis

Potassium-induced cardiac resetting technique for persistent ventricular tachycardia and fibrillation after aortic declamping

We report a technique of injecting a high concentration of potassium chloride into the aorta root to resolve refractory ventricular tachycardia after aortic declamping, which occurs occasionally in open heart surgeries. Using this technique, normal sinus rhythm can be restored without the need for defibrillation and aortic clamping.

Does stentless aortic valve implantation increase perioperative risk? A critical appraisal of the literature and risk of bias analysis

Stentless aortic valve replacement has potential benefits in terms of valve hemodynamics and clinical outcomes, although these may be offset by greater technical complexity of implantation with longer cardiopulmonary bypass and cross-clamp times compared with stented valves. Meta-analyses of the small number of published randomized trials have been limited by their lack of critical synthesis of the literature, including evaluation of the Risk of Bias. Our objective was to determine whether stentless aortic valves increase perioperative risk of mortality. We also examined secondary clinical outcomes of neurological, renal and respiratory complications as well as hemodynamic changes reported by studies following implantation of the two types of aortic prosthesis. The methodology used to answer this question was a rigorous meta-analysis of randomized controlled trials, using bias-assessment techniques designed to address limitations of conventional meta-analysis. Our findings show that many of the existing randomized trials have a high or uncertain risk of bias. Analysis of studies with low risk of bias reveals that stentless valves do not increase perioperative risk in terms of 30-day mortality and morbidity though neither do they exhibit benefits in hemodynamics or clinical outcomes compared with stented valves. Larger, more stringent randomized studies would be required to identify any robust clinical difference.

Valve replacement for aortic stenosis normalizes subendocardial function in patients with normal ejection fraction

AIMS

Long-standing aortic stenosis (AS) causes various degrees of left ventricular (LV) dysfunction, which may improve after valve replacement. The aim of this study was to assess the nature of LV subendocardial abnormalities in AS and their response to valve replacement (AVR).

METHODS AND RESULTS

We studied 41 consecutive symptomatic patients (age 64 +/- 13 years) with severe AS, normal LV ejection fraction (EF), but no obstructive coronary artery disease before, a week after AVR, and 6 months after AVR. LV subendocardial function was studied from recordings of long-axis M-mode (amplitude), tissue-Doppler (myocardial velocities) and speckle tracking (myocardial strain) echocardiographic techniques. Results were compared with those from 20 age- and gender-matched controls. In patients, LV dimensions and markers of asynchrony, total isovolumic time (t-IVT), and Tei index were not different from controls before AVR and remained unchanged afterwards. LV lateral long-axis amplitude, as well as lateral and septal systolic velocities and strain, were reduced (P < 0.001 for all) and E/E' was modestly raised. Lateral long-axis amplitude, systolic and diastolic velocities normalized within a week of AVR but strain lagged behind until 6 months later. The reduced septal long-axis amplitude remained permanently unchanged (NS) despite the early normalization of its systolic velocities (P < 0.001) and strain (P < 0.001). LV mass normalized at 6 months after AVR (P < 0.005).

CONCLUSIONS

In patients with severe AS and maintained LV ejection fraction, subendocardial function is globally abnormal showing reduced amplitude of motion, velocities, and strain. The different response of its components suggests an evidence for differential reverse remodelling, irrespective of myocardial mass regression.

Surgical outcomes and post-operative changes in patients with significant aortic stenosis and severe left ventricle dysfunction

Little is known regarding long-term survival and changes in systolic function following surgery after the occurrence of a severe left ventricular (LV) dysfunction in patients with severe aortic stenosis. Inclusion criteria were an aortic valve area less than 1 cm(2) and an LV ejection fraction (EF) less than 35%. Between January 1990 and July 2007, 41 (male: 30) patients were identified. The pre-operative mean EF and mean aortic valve area were 26.7+/-6.1% and 0.54+/-0.2 cm(2), respectively. Concomitant coronary artery bypass surgery was performed in 8 patients (19.6%). Immediate post-operative echocardiogram showed to be much improved in LV EF (27.2+/-5.5 vs. 37.4+/-11.3, P<0.001), LV mass index (244.2+/-75.3 vs. 217.5+/-71.6, P=0.006), and diastolic LV internal diameter (62.5+/-9.3 vs. 55.8+/-9.6, P<0.001). Post-operative LV changes were mostly complete by 6 months, and were maintained thereafter. There was one in-hospital mortality (2.4%) and 12 late deaths including one patient diagnosed with malignancy in whom LV function was normal. Multivariate analysis showed pre-operative atrial fibrillation and NYHA FC IV to be significant risk factors for cardiac-related death. Aortic valve replacement in patients with significant aortic stenosis and severe LV dysfunction showed acceptable surgical outcomes. Moreover, LV function improved significantly in many patients.

Low-flow, low-gradient aortic stenosis: from evaluation to treatment

PURPOSE OF REVIEW

Valve replacement improves symptoms and survival in symptomatic severe aortic stenosis. Low-flow, low-gradient aortic stenosis, however, is an especially challenging subset as valve replacement has a significant risk, and may fail to alleviate symptoms or improve left ventricular function. This article reviews the potential problems in evaluating aortic stenosis severity in low-flow, low-gradient aortic stenosis, the utility of dobutamine challenge to identify patients most likely to benefit from surgery, and the factors predicting patient outcome.

RECENT FINDINGS

Low-flow, low-gradient aortic stenosis consists of a heterogeneous group of patients with 'true' severe aortic stenosis, in whom afterload mismatch results from a severely stenotic valve; and 'pseudo-severe' aortic stenosis, where the valve is only mildly or moderately stenotic, but appears severe due to limitations in determining disease severity under low-flow conditions. Valve replacement is likely to benefit the former group, but may have little benefit to the latter. Dobutamine challenge can distinguish 'true' and 'pseudo-severe' aortic stenosis, and can evaluate contractile reserve, one of the strongest predictors of patient outcome. Strategies to avoid prosthesis-patient mismatch should be considered to optimize postoperative outcome.

SUMMARY

Dobutamine challenge can identify low-flow, low-gradient aortic stenosis patients most likely to benefit from valve replacement and provides important prognostic information on the operative risks and long-term outcome.

The bioprosthesis type and size influence the postoperative incidence of permanent pacemaker implantation in patients undergoing aortic valve surgery

BACKGROUND

Long-standing aortic stenosis (AS) causes significant progressive left ventricular dysfunction and may result in subendocardial ischaemia and conduction disorders. Though stentless bioprosthesis show better haemodynamic profiles compared with stented, yet debate exists about the differential effects of valve substitutes on the incidence of permanent pacemaker (PPM) implantation following aortic valve replacement (AVR).

METHODS

510 consecutive patients aged 65-77 years with predominant AS accepted for isolated non-emergent AVR (360 received stented and 150 stentless) were studied over three years period. A stepwise logistic regression analysis was used and statistical significance was accepted at P < 0.05.

RESULTS

Mean age +/- standard deviation for the stented group was 70.43 +/- 7.2 and the stentless was 61.7 +/- 12.3. Perioperative (30-day) mortality was 1% (5 of the 510 patients). Smaller aortic prosthesis size was identified as a significant predictors of hospital mortality [univariate and multivariate analysis (P < 0.05)]. Risk factors identified for PPM by univariate analysis were: preoperative: age, left atrial enlargement (LAE), MI, left bundle branch block (LBBB), poor ejection fraction < 35% (P < 0.05), postoperative; bypass time > 100 min with x-clamp time > 70 min, concomitant aortic surgery and prosthetic valve size < or = 21 mm (P < 0.05). Multivariate analysis identified the preoperative MI (P = 0.003), poor ejection fraction < 35% (P = 0.007), LAE, (P = 0.001) and LBBB (P = 0.002), the perioperative variables; bypass time > 100 min with x-clamp time > 70 min (P < 0.001) and prosthetic valve size < or = 21 mm (P = 0.003). Test of interaction analysis identified valve type as an important predictor of PPM (P = 0.01).

CONCLUSIONS

The results demonstrated that where stentless valves required longer bypass and cross clamp times, more stented valves were small (< 21 mm, P < 0.05). In précis, this suggests that prevalence of PPM seems to be dependent on the size and type of bioprosthesis used in patients undergoing isolated AVR and this incidence of PPM is twice in stentless group (18% vs. 9.1%, P = 0.01).