TITLE:
Prognostic implication of the coronary microvascular dysfunction in patients with isolated left bundle branch block
AUTHORS:
Francisco J. Rodríguez Rodrigo, Juan Medina Peralta, Eddy Velásquez Arias, Ana Alegría Barrero, Teresa San Agustín Lascorz, Elena Pérez Pereira, Adriana Rodríguez Chaverri
KEYWORDS:
Microvascular Dysfunction; Isolated Left Bundle Branch Block; Left Ventricular Dysfunction
JOURNAL NAME:
World Journal of Cardiovascular Diseases,
Vol.4 No.2,
February
14,
2014
ABSTRACT: The present study aims to determine the influence of
microvascular dysfunction (MVD) in the prognosis of patients presenting
isolated left bundle branch block (LBBB). Methods: We studied 30 patients
(pts), 22 males, 8 females, mean age 57 ± 4 years, with isolated LBBB, with a
mean follow up of 48 ± 6 months. The control group consisted of 20 healthy
individuals, 12 males, mean age 52 ± 10 years. Both groups were screened for
cardiovascular risk factors (RF); they also had an echocardiogram and Coronary
CT Scan, ruling out both structural heart disease and obstructive lesions of the epicardial coronary arteries.
A myocardial perfusion study was then performed, with two groups
emerging according to these results: Group A, 8 pts (26%), with reversible perfusion defects, in which the diagnosis of MVD was suspected, and Group B, 22 pts (74%), with either
normal perfusion or minor septal/apical reversible defects (related to LBBB).
All Group A pts, and 9 of the Group B pts, underwent coronary arteriography,
with intracoronary acetylcholine and nitroglycerine infusion, thus evaluating vasomotor
response as endothelium dependent (acetylcholine) or endothelium independent
(nitroglycerine). During follow up, we reviewed functional class, 12 lead ECG
and echocardiogram on a yearly basis. Results: All Group A patients had an abnormal acetylcholine
response; only three of them had abnormal response to nitroglycerine infusion,
suggesting endothelium dependent MVD. Of those in Group B, only one patient had
abnormal acetylcholine response. At the end of the follow up period, 3 pts (37%) in Group A,
showed functional class decrease vs 5 pts (22%) of
those in Group B. In Group
A, a significant increase of End Diastolic Left Ventricle Diameter (EDLVD) was
found (51.6 ± 3.6 vs 59.3 ± 6.8 mm; p variation. In neither group major
complications (death, heart failure admissions) were found. Conclusion: We confirm the association
between MVD and a worse clinical prognosis
in isolated LBBB patients. Repeated ischemia and myocardial fibrosis are
highlighted as possible physiopathological mechanisms, precluding a progressive
left ventricular function decrease, with a higher mortality and arrhythmia
risk. Endothelial function preserving strategies, both preventive and
therapeutic, might be useful in improving LBBB with MVD patient’s prognosis.