Prognostic Value of Coronary Flow Reserve Obtained on Dobutamine Stress Echocardiography and its Correlation with Target Heart Rate

Abstract

Background:: Normal coronary flow velocity reserve (CFVR) (≥ 2) obtained in the left anterior descending coronary artery (LAD) from transthoracic echocardiography is associated with a good prognosis, but there is no study correlating CFVR with submaximal target heart rate (HR).

Objective:: To evaluate the prognostic value of CFVR obtained in the LAD of patients with preserved (>50%) left ventricular ejection fraction (LVEF) who completed a dobutamine stress echocardiography (DSE), considering target HR.

Methods:: Prospective study of patients with preserved LVEF and CFVR obtained in the LAD who completed DSE. In Group I (GI = 31), normal CFVR was obtained before achieving target HR, and, in Group II (GII = 28), after that. Group III (G III=24) reached target HR, but CFVR was abnormal. Death, acute coronary insufficiency, coronary intervention, coronary angiography without further intervention, and hospitalization were considered events.

Results:: In 28 ± 4 months, there were 18 (21.6%) events: 6% (2/31) in GI, 18% (5/28) in GII, and 46% (11/24) in GIII. There were 4 (4.8%) deaths, 6 (7.2%) coronary interventions and 8 (9.6%) coronary angiographies without further intervention. In event-free survival by regression analysis, GIII had more events than GI (p < 0.001) and GII (p < 0.045), with no difference between GI and GII (p = 0.160). After adjustment, the only difference was between GIII and GI (p = 0.012).

Conclusion:: In patients with preserved LVEF and who completed their DSE, normal CFVR obtained before achieving target HR was associated with better prognosis.

Fundamento:: A reserva de velocidade de fluxo coronariano (RVFC) adequada (≥ 2) obtida na artéria descendente anterior (ADA) através do ecocardiograma transtorácico associa-se a bom prognóstico, mas não há estudo correlacionando-a com a frequência cardíaca (FC) alvo (submáxima).

Objetivo:: Avaliar o valor prognóstico da RVFC obtida na ADA de pacientes com fração de ejeção do ventrículo esquerdo (FEVE) preservada (>50%) e ecocardiograma sob estresse com dobutamina (EED) concluído, considerando a FC alvo submáxima.

Métodos:: studo prospectivo de pacientes com FEVE preservada e RVFC obtida na ADA durante EED concluído. No Grupo I (GI=31), a RVFC adequada foi obtida antes de se atingir a FC alvo, e no Grupo II (G II=28), após. O Grupo III (G III=24) atingiu a FC alvo, mas a RVFC foi inadequada. Foram considerados eventos: óbito, insuficiência coronariana aguda, intervenção coronariana, coronariografia sem intervenção subsequente e internamento hospitalar.

Resultados:: Em 28 ± 4 meses, ocorreram 18 (21,6%) eventos, sendo 6% (2/31) no GI, 18% (5/28) no GII e 46% (11/24) no GIII. Foram 4 (4,8%) óbitos, 6 (7,2%) intervenções coronarianas e 8 (9,6%) coronariografias sem intervenção subsequente. Na sobrevida livre de eventos pela análise de regressão, GIII apresentou mais eventos do que GI (p < 0,001) ou GII (p < 0,045), não havendo diferença entre GI e GII (p = 0,160). Após o ajustamento, foi mantida a diferença apenas entre GIII e GI (p = 0,012).

Conclusão:: Em pacientes com FEVE preservada e EED concluído, a RVFC adequada obtida antes da FC alvo associou-se ao melhor prognóstico.

Figure 1

Male patient with target heart rate (HR) of 142 bpm. Figure 1A shows Doppler assessment in the left anterior descending coronary artery (LAD) at baseline. Figure 1B, during dobutamine stress echocardiography (DSE), dose = 20 µg.kg^-1.min^-1 and HR = 68 bpm, shows normal (=2.78) and early (obtained before achieving target HR) coronary flow velocity reserve (CFVR). Normal left ventricular contractility during the entire exam.

Figure 2

Male patient with target heart rate (HR) of 140 bpm. Figure 2A shows Doppler assessment in the left anterior descending coronary artery (LAD) at baseline. Figure 2B, during dobutamine stress echocardiography (DSE), dose = 20 µg.kg^-1.min^-1 and HR = 99 bpm, shows normal (2.15) and early coronary flow velocity reserve (CFVR), which increases progressively, even after reaching target HR (Figure 2D). Normal left ventricular contractility during the entire exam.

Figure 3

A) Kaplan-Meier regression analysis of event-free survival by group. Normal (= 2) coronary flow velocity reserve (CFVR) was obtained before (Group I) and after (Group II) reaching submaximal target heart rate. In Group III, CFVR was abnormal. Group III differed from Group I and Group II, but there was no difference between Group I and Group II. B) Survival for the event adjusted for age and ejection fraction, by use of Cox regression and Wald statistics. Group III and Group I remained different, and the better event-free survival was maintained only in Group I.