Cardiac resynchronization therapy for low‐flow,low‐gradient aortic stenosis

Low‐flow, low‐gradient aortic stenosis is a heterogeneous entity that encompasses truly severe aortic stenosis as well as mild‐to‐moderate aortic stenosis in which aortic valve orifice area is severely reduced primarily due to left ventricular (LV) contractile dysfunction. Under such circumstances the capacity of the LV to generate stroke‐work is severely compromised. In this case report, we describe a patient with severe LV dysfunction and ventricular dyssynchrony due to right ventricular pacing who presented with decompensated heart failure in the setting of low‐flow, low‐gradient aortic stenosis. We discuss the management of this high‐operative‐risk patient, who ultimately underwent upgrading of his dual chamber pacemaker to a biventricular pacemaker with significant echocardiographic, haemodynamic, and clinical improvement.     

Low flow low gradient aortic stenosis: clinical pathways

Aortic stenosis patients with severe LV dysfunction and low cardiac output present with relatively low transvalvular gradients. It is difficult to distinguish them from aortic sclerosis and LV dysfunction with low cardiac output. The former condition is severe AS with LV dysfunction and latter is primarily a contractile dysfunction. Dobutamine stress echocardiogram is key to diagnosis.AS with LV dysfunction associated with preserved contractile reserve benefit from valve replacement and those without contractile reserve needs critical evaluation on a case to case basis. Patients of AS with LV dysfunction with associated coronary artery disease need coronary angiograms to decide regarding need for valve replacement with bypass surgery. A subset of AS patients have low flow, low mean gradients with preserved ejection fraction in whom one must evaluate global hemodynamic load to assess ventriculo-arterial impedence.In this review an approach to the clinical pathways for assessment of low flow, low gradient aortic stenosis has been discussed.     

Reduced high-frequency QRS components in electrocardiogram leads facing an area of the heart with intraventricular conduction delay due to bundle branch block

Background

The mechanisms underlying high-frequency QRS components (HF-QRS) are incompletely understood. One theory is that HF-QRS are related to the conduction velocity of the heart. The purpose was to test this hypothesis by comparing HF-QRS in patients with left or right bundle branch block (LBBB and RBBB, respectively) to those in healthy subjects and in patients with ischemic heart disease (IHD).

Methods

Twenty-two patients with LBBB, 19 patients with RBBB, 63 normal subjects, and 64 patients with IHD were included. Twelve-lead electrocardiograms were analyzed in the frequency interval 150 to 250 Hz.

Results

The study showed reduced HF-QRS in patients with LBBB compared with healthy subjects and patients with IHD. The difference, however, was small in lead V₁ and V₂. In patients with RBBB, no differences in HF-QRS could be detected except in few leads; among those is lead V₁.

Conclusion

The results support the theory that HF-QRS are related to the conduction velocity of the heart.     

Transcatheter aortic valve implantation outcomes in patients with low flow low gradient aortic stenosis

BackgroundSome studies suggest that patients with low flow low gradient (LF-LG) aortic stenosis (AS) may achieve worse results after undergoing transcatheter aortic valve implantation (TAVI).PurposeTo compare outcomes between LF-LG AS and high gradient (HG) AS patients submitted to TAVI.MethodsInclusion of 480 consecutive patients who underwent TAVI between 2008 and 2020 at a single tertiary center. Patients were divided into high gradient AS and LF-LG AS; and baseline characteristics and outcomes after the procedure were collected and compared between groups.ResultsPatients with LF-LG AS had worse baseline characteristics, with higher Society of Thoracic Surgeons score (p=0.008), New Euroscore II (p<0.0001), and NT pro-natriuretic peptide B (p=0.001), more frequent left ventricular ejection fraction (LVEF) <40% (p<0.0001), coronary artery disease (p<0.0001), including previous myocardial infarction (p=0.002) and coronary artery bypass graft (p<0.0001), poor vascular accesses (p=0.026) and periprocedural angioplasty (p=0.038). In a multivariate analysis, adjusted to differences in baseline characteristics, LF-LG AS was associated with worse functional class at one year (p=0.023) and in the long-term (p=0.004) and with heart failure hospitalizations at one year and in the long-term (p=0.001 and p<0.0001). In a sub-analysis including only patients with LF-LG AS, those with LVEF <40% had the worst outcomes, with more global (p=0.035) and cardiovascular (p=0.038) mortality.ConclusionPatients with LF-LG AS have worse short and long-term outcomes, even when adjusted for baseline characteristic differences. The sub-group of patients with LVEF <40% have the most ominous global outcomes.     

Outcomes and survival with aortic valve replacement compared with medical therapy in patients with low-, moderate-, and severe-gradient severe aortic stenosis and normal left ventricular ejection fraction

Background: This study determined outcomes and survival with aortic valve replacement (AVR) versus medical therapy in patients with normal left ventricular ejection fraction (LVEF) with severely reduced aortic valve areas (AVA) but nonsevere mean gradients. Methods: We identified 248 aortic stenosis (AS) patients with LVEF ≥ 50% and echocardiographic AVA < 1.0 cm². Group 1 had low‐gradient: <30 mmHg mean gradient; group 2 (moderate: 30 to 40 mm Hg); and group 3 (severe: >40 mm). Results: There were 94, 87, and 67 patients in groups 1, 2, and 3. Incidence of death in groups 1, 2, and 3 were 55%, 39%, and 39% (P not significant). Incidence of AVR in groups 1, 2, and 3 were 23%, 53%, and 49% (P < 0.0001 for group 1 vs. 2; P = 0.0003 for group 1 vs. group 3). Incidence of AVR or death was 71%, 77%, and 76% (P not significant). AVR (hazard ratio = 0.30; 95% CI, 0.18, 0.51; P < 0.0001) and mitral annular calcification (hazard ratio = 2.33; 95% CI, 1.40, 3.88; P = 0.001) were independently associated with time to mortality. Kaplan–Meier curves for time to death did not differ significantly among the three groups. Kaplan–Meier survival curves for patients with and without AVR showed patients in all three groups who underwent AVR had significantly greater survival. Conclusion: Among patients with normal LVEF and AVA < 1.0 cm², overall survival does not differ among those with low‐, moderate‐, or severe‐aortic valve gradients. Survival is significantly improved with AVR, regardless of gradient. (Echocardiography 2011;28:378‐387)     

Outcomes of patients with low‐pressure aortic gradient undergoing transcatheter aortic valve implantation

Background: The risk/benefit balance of transcatheter aortic valve implantation (TAVI) in patients with low‐gradient aortic stenosis (LGAS) remains to be well defined. Aim of the study was to investigate the impact of LGAS in patients undergoing TAVI. Methods: Medline, Cochrane Library, and Scopus were searched for articles reporting outcome of patients with LGAS undergoing TAVI. The primary endpoint was 12‐months all‐cause mortality and the secondary endpoint was 30‐day all‐cause mortality. Using event‐rates as dependent variable, a meta‐regression was performed to test for interaction between baseline clinical features (age, gender, diabetes mellitus, coronary artery disease, left ventricular ejection fraction (LVEF) and type of implanted valve) and transaortic gradient for the primary endpoint. Results: Eight studies with a total of 12,589 patients were included. Almost one‐third of the patients presented with LGAS (27.3%: 24.4–29.2). Median LVEF was 48% in patients with LGAS and 56% in patients with high‐gradient AS. Patients with LGAS were more likely to have diabetes mellitus, previous coronary artery disease, higher mean Logistic EuroSCORE, and lower EF. At 12 (12–16.6) months, low transaortic gradient emerged as independently associated with all‐cause death, both if evaluated as a dichotomous and continuous value (respectively OR 1.17; 1.11–1.23 and OR 1.02; 1–1.04, all CI 95%). Clinical variables, including EF did not affect this result. Conclusions: In a population of TAVI patients, LGAS appears to be independently related to dismal prognosis. © 2016 Wiley Periodicals, Inc.     

Left ventricular electromechanical delay in patients with heart failure and normal QRS duration and in patients with right and left bundle branch block.

AIMS: We sought to define the reference values of intra-left ventricular (LV) electromechanical delay (EMD), and to assess the prevalence (and pattern) of intra-LV dyssynchrony in patients with heart failure (HF) and normal QRS and in patients with right and left bundle branch block. METHODS AND RESULTS: We used tissue Doppler imaging echocardiography and a six-LV wall model to study LV EMD in 103 patients [41 with HF and normal QRS, 22 with right bundle branch block (RBBB), and 40 with left bundle branch block (LBBB)], and in 59 controls. In controls, the median intra-LV EMD was 17 ms, (inter-quartile range 13-30); 95% of controls had a value < or =41 ms. Patients showed a longer intra-LV EMD than controls: 33 ms (20-57) in patients with normal QRS, 32 ms (23-50) in RBBB patients, and 50 ms (30-94) in LBBB patients. Intra-LV dyssynchrony (defined as intra-LV EMD >41 ms) was present in 39, 36, and 60% of the patients, respectively. On average, HF patients showed the same pattern of activation as controls, from the septum to the posterior wall, but activation times were significantly prolonged. In RBBB patients the activation sequence was directed from inferior to anterior and in LBBB from anterior to inferior wall. CONCLUSIONS: Left ventricular dyssynchrony was present in several patients with HF and normal QRS, and in patients with RBBB; conversely, 40% of LBBB patients showed values of LV EMD within the normal range. Left ventricular activation sequence was different between groups. Assessment of LV synchronicity by means of imaging techniques may be more important than QRS duration or morphology in selecting patients for cardiac resynchronization treatment.