Não é de hoje que falamos em Paradoxal Low Flow/Low Gradient Aortic Stenosis (FEVE preervada). Mas parece que este assunto fica marginal nas discussões, mesmo entre os ecocardiografistas! A utilização exclusiva do gradiente para graduação da estenose aórtica é falha, e não deve ser a única variável analisada.
Recentemente, acompanhei paciente com estenose aórtica grave, com hipertrofia concêntrica grave, com AVA estimada em 0,6cm2 por equação da continuidade, apresentando gradiente de pico VE/Ao 53mmHg e médio de 33mmHg. Como a paciente apresentava inúmeras comorbidades (DPOC, IRC não dialítica, coronariopatia estáve;), foi encaimnhada para implante percutâneo de prótese aórtica. Foi solicitado por médico assistente CATE, e aproveitou-se para medir os gradientes VE/AO. Como o gradiente foi de 27mmHg (pico/pico), foi considerado como estenose moderada e contra-indicado o procedimento!!! Esta paciente,em um intervalo de 3 meses, deu entrada 7 vezes na unidade de emergência com edema agudo de pulmão!!! Repeti 5 vezes este mesmo exame. Conversado com equipe de Hemodinâmica e médico assistente e finalmente concordado com procedimento!
Liege, Belgium - Some asymptomatic patients previously thought to have only moderate aortic stenosis actually have a poor prognosis, a study of a new aortic stenosis classification system has found [
1].
"We need to classify the aortic stenosis not only according to the valve area and the gradient, but also according to the flow,"
Dr Patrizio Lancellotti (University of Liege, Belgium) told
heartwire.
Lancellotti and colleagues evaluated 150 asymptomatic aortic stenosis patients using normal exercise test results with transthoracic echocardiography and B-type natriuretic peptide tests. The patients were categorized into four groups based on left-ventricular flow and aortic valve pressure gradient levels. The cutoff for low vs normal flow was 35 mL/m2, and the cutoff for low vs high gradient was 40 mm Hg.
Lancellotti explained to
heartwire that under existing guidelines an aortic valve with low flow and a low gradient would be considered to have only a moderate stenosis, but the study shows that patients with low flow and a low gradient had an even worse prognosis than those in the more obvious low-flow/high-gradient group [
2].
In an accompanying editorial,
Drs Frank Flachskampf and
Mohammad Kavianipour (Uppsala University, Sweden) explain that the study by Lancellotti et al "re-emphasizes the utility of close follow-up (six- to 12-month intervals) and liberal use of exercise to confirm lack of symptoms" and "calls for a more complete evaluation of aortic stenosis severity than just the peak and mean gradient, and ejection fraction" [
3].
Not merely "moderate" stenosis
In the study, two-year cardiac event-free survival was 83% for patients with normal flow and a low gradient, 44% for patients with normal flow and a high gradient, 30% for patients with low flow and a high gradient, and 27% for patients with a low flow and a low gradient (p<0.0001). Multivariable analysis showed that low flow/low gradient patients were 5.26-times more likely to have an event than patients with normal flow and a high gradient (p=0.046).
Low-flow/low-gradient patients are rare—only 7% of this study population—but "this is really important," Lancellotti said. "We cannot miss this diagnosis, because if we do, when we have the patients in front of us, we will face the problem of saying that 'ok, this is not important . . . This is a moderate stenosis.'" Earlier studies show that these patients are less frequently referred to surgery than patients with normal flow and a high gradient, he said. But "it's really important to recognize this entity, and we cannot deny surgery to these asymptomatic patients. We cannot deny close follow-up because their prognosis is totally impaired," Lancellotti said.
The low-flow/low-gradient patients in this study also had preserved left-ventricular ejection fraction and an aortic valve area <1 cm2. These so-called "paradoxical" low-flow aortic stenosis patients also tend to have more pronounced LV concentric remodeling, a smaller left-ventricular cavity, increased global left-ventricular afterload, intrinsic myocardial dysfunction, and a "dismal prognosis," the authors note. This cluster of findings suggests that these patients are most likely at an advanced stage of disease, they say.
However, the patients with normal flow and a low gradient had significantly lower B-type natriuretic peptide (BNP) levels than those with low flow and a high gradient or those with low flow and a low gradient. "This observation emphasizes that risk scores might fail to predict the actual risk on an individual basis," Lancellotti et al note. This finding might be linked to "exhausted BNP production", higher BNP clearance, or diminished BNP release secondary to reduced left-ventricular wall stress.
Identifying at-risk patients
Lancellotti said that his group's next step is to find a way to use exercise echo data to identify the subset of patients with low flow who are at increased risk of CV events over the short term. Echo "could perhaps predict, in a more appropriate way, the outcomes, compared to BNP, longitudinal function, and left-ventricular area."
Flachskampf and Kavianipour add that "if confirmed, [low-flow/low-gradient] patients should perhaps be further evaluated with regard to LV longitudinal function and BNP. Clear guidance as to which cutoffs might prompt valve replacement is missing so far, but studies like the present report help in making informed individual decisions."
Recomendo a todos uma olhadinha neste trabalho:
Paradoxical Low-Flow, Low-Gradient Severe Aortic Stenosis Despite Preserved Ejection Fraction Is Associated With Higher Afterload and Reduced Survival
Zeineb Hachicha, MD; Jean G. Dumesnil, MD; Peter Bogaty, MD; Philippe Pibarot, DVM, PhD
Background: Recent studies and current clinical observations suggest that some patients with severe aortic stenosis on the basis of aortic valve area may paradoxically have a relatively low gradient despite the presence of a preserved left ventricular (LV) ejection fraction. The objective of the present study was to document the prevalence, potential mechanisms, and clinical relevance of this phenomenon.
Methods and Results: We retrospectively studied the clinical and Doppler echocardiographic data of 512 consecutive patients with severe aortic stenosis (indexed aortic valve area 0.6 cm2 m 2) and preserved LV ejection fraction 50%). Of these patients, 331 (65%) had normal LV flow output defined as a stroke volume index 35 mL m2, and 181 (35%) had paradoxically low-flow output defined as stroke volume index 35 mL m 2. When compared with normal flow patients, low-flow patients had a higher prevalence of female gender (P 0.05), a lower transvalvular gradient (32+/- 17 versus 40 +/- 15 mm Hg; P 0.001), a lower LV diastolic volume index (52+/- 12 versus 59+/- 13 mL m 2; P 0.001), lower LV ejection fraction (62 +/- 8% versus 68,+/- 7%; P 0.001), a higher level of LV global afterload reflected by a higher valvulo-arterial impedance (5.3 +/- 1.3 versus 4.1 0.7 mm Hg · mL 1 · m 2; P 0.001) and a lower overall 3-year survival (76% versus 86%;
P0.006). Only age (hazard ratio, 1.04; 95% CI, 1.01 to 1.08; P0.025), valvulo-arterial impedance 5.5 mm Hg · mL 1 · m 2 (hazard ratio, 2.6; 95% CI, 1.2 to 5.7; P0.017), and medical treatment (hazard ratio, 3.3; 95% CI, 1.8 to 6.7; P0.0003) were independently associated with increased mortality.
Conclusion: Patients with severe aortic stenosis may have low transvalvular flow and low gradients despite normal LV ejection fraction. A comprehensive evaluation shows that this pattern is in fact consistent with a more advanced stage of the disease and has a poorer prognosis. Such findings are clinically relevant because this condition may often be misdiagnosed, which leads to a neglect and/or an underestimation of symptoms and an inappropriate delay of aortic valve replacement surgery.
(Circulation. 2007;115:2856-2864.)
