High Prevalence of Severe Aortic Stenosis in Low-Flow State Associated With Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) is a low-flow state and may underestimate aortic stenosis (AS) severity. Single-high Doppler signals (HS) consistent with severe AS (peak velocity ≥4 m/s or mean gradient ≥40 mm Hg) are averaged down in current practice. The objective for the study was to determine the significance of HS in AF low-gradient AS (LGAS).

METHODS

One thousand five hundred forty-one patients with aortic valve area ≤1 cm² and left ventricular ejection fraction ≥50% were identified and classified as high-gradient AS (HGAS) (≥40 mm Hg) and LGAS (<40 mm Hg), and AF versus sinus rhythm (SR). Available computed tomography aortic valve calcium scores (AVCS) were retrieved from the medical record. Outcomes were assessed.

RESULTS

Mean age was 76±11 years, female 47%. Mean gradient was 51±12 in SR-HGAS, 48±10 in AF-HGAS, 31±5 in SR-LGAS, and 29±7 mm Hg in AF-LGAS, all P≤0.001 versus SR-HGAS; HS were present in 33% of AF-LGAS. AVCS were available in 34%. Compared with SR-HGAS (2409 arbitrary units; interquartile range, 1581-3462) AVCS were higher in AF-HGAS (2991 arbitrary units; IQR1978-4229, P=0.001), not different in AF-LGAS (2399 arbitrary units; IQR1817-2810, P=0.47), and lower in SR-LGAS (1593 arbitrary units; IQR945-1832, P<0.001); AVCS in AF-LGAS were higher when HS were present (P=0.048). Compared with SR-HGAS, the age-, sex-, comorbidity index-, and time-dependent aortic valve replacement-adjusted mortality risk was higher in AF-HGAS (hazard ratio=1.82 [1.40-2.36], P<0.001) and AF-LGAS with HS (hazard ratio=1.54 [1.04-2.26], P=0.03) but not different in AF-LGAS without HS or SR-LGAS (both P=not significant).

CONCLUSIONS

Severe AS was common in AF-LGAS. AVCS in AF-LGAS were not different from SR-HGAS. AVCS were higher and mortality worse in AF-LGAS when HS were present.

Dobutamine stress echocardiography in low-flow, low-gradient aortic stenosis with concomitant severe functional mitral regurgitation: a case report

Background 

Dobutamine stress echocardiography (DSE) in classical low-flow, low-gradient (LFLG) aortic stenosis (AS) is recommended in recent guidelines to differentiate true-severe AS from pseudo-severe AS. However, DSE for patients with concomitant significant mitral regurgitation (MR) is often inaccurate or inconclusive.

Case summary 

A 73-year-old man with a history of coronary artery bypass grafting was referred to our institution with congestive heart failure. Transthoracic echocardiogram showed severe functional MR and LFLG AS. The results of DSE to determine the severity of AS were inconclusive owing to the absence of flow reserve, usually defined as stroke volume increase of ≥20%. In addition, calcium score by computed tomography scan was also inconclusive. Our heart team decided to reassess the severity of AS after percutaneous edge-to-edge mitral valve repair (PMVR), considering the patient’s high surgical risk. Percutaneous edge-to-edge mitral valve repair was uneventful, resulting in marked reduction of MR from severe to trivial. Dobutamine stress echocardiography after PMVR revealed true-severe AS with the presence of flow reserve. Transcatheter aortic valve implantation (TAVI) was performed, and the patient ambulatorily discharged.

Discussion 

The coexistence of significant AS may lead to overestimation of the severity of MR, and reportedly, concomitant MR improves in the majority of patients after TAVI, especially MR of functional aetiology. However, the coexistence of significant MR often leads to inconclusive DSE results because dobutamine stress may worsen MR and fail to increase the stroke volume. In our case, DSE after PMVR was useful to diagnose the true-severe AS for the patient with LFLG AS and severe functional MR.