title: Left Bundle Branch Block Negatively Affects Coronary Flow Velocity Reserve and Myocardial Contractile Reserve in Nonischemic Dilated Cardiomyopathy.
abstract: BACKGROUND
  Coronary flow velocity reserve (CFVR) of the left anterior descending coronary artery (LAD) and myocardial contractile reserve are often impaired in nonischemic dilated cardiomyopathy (DCM). Whether they are affected by the presence of left bundle branch block (LBBB) remains unaddressed. The aim of the study was to investigate how LBBB influences CFVR of the LAD and myocardial contractile reserve in patients with DCM.
  
  
  METHODS
  One hundred eighty-one patients with DCM (116 men; mean age, 63 ± 12 years) underwent high-dose dipyridamole (0.84 mg/kg over 6 min) stress echocardiography with CFVR evaluation of the LAD by Doppler. All patients had ejection fractions < 40% (mean, 31 ± 8%) and angiographically normal or near normal coronary arteries. CFVR was defined as the ratio between hyperemic peak and basal peak diastolic coronary flow velocities. CFVR > 2.0 was considered normal. Inotropic reserve was defined as rest-stress variation in wall motion score index ≥ 0.20. This was a prospective analysis of an unselected sample consecutively enrolled and retrospectively selected.
  
  
  RESULTS
  The study group was separated on the basis of presence (n = 122) or absence (n = 59) of LBBB. Patients with LBBB were older (64 ± 11 vs 59 ± 12 years, P = .004) and had reduced resting ejection fractions (30 ± 9% vs 33 ± 7%, P = .02), CFVR of the LAD (1.96 ± 0.41 vs 2.23 ± 0.73, P = .001), and myocardial contractile reserve (variation in wall motion score index, -0.18 ± 0.17 vs -0.33 ± 0.28; P < .001). On multivariate logistic regression analysis, resting ejection fraction (hazard ratio [HR], 1.15; 95% CI, 1.03-1.29; P = .01), smoking habit (HR, 2.63; 95% CI, 1.23-5.62; P = .01), and LBBB (HR, 2.29; 95% CI, 1.05-5.04; P = .04) were independently associated with reduced CFVR, while restrictive transmitral pattern (HR, 2.56; 95% CI, 1.18-5.55; P = .02), end-diastolic volume (HR, 0.98; 95% CI, 0.67-0.99; P = .02), and LBBB (HR, 2.20; 95% CI, 1.11-4.34; P = .02) independently predicted reduced myocardial contractile reserve.
  
  
  CONCLUSIONS
  CFVR during vasodilator stress echocardiography is a suitable tool for assessing microvascular dysfunction in routine clinical practice. Patients with DCM and LBBB show more severe forms of microvascular dysfunction, which is related to worse left ventricular function and lack of contractile reserve. Therapeutic interventions to restore microvascular function may improve left ventricular function parameters in patients with DCM.
authors.affiliation: Division of Cardiology, Fatebenefratelli Hospital, Benevento, Italy. Electronic address: qciampi@gmail.com.
authors.forename: Quirino
authors.initials: Q
authors.lastname: Ciampi
authors.affiliation: Division of Cardiology, San Luca Hospital, Lucca, Italy.
authors.forename: Lauro
authors.initials: L
authors.lastname: Cortigiani
authors.affiliation: CNR, Institute of Clinical Physiology, Pisa, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Pratali
authors.affiliation: Department of Cardiology, Dell'Angelo Hospital, Mestre, Italy.
authors.forename: Fausto
authors.initials: F
authors.lastname: Rigo
authors.affiliation: Division of Cardiology, Fatebenefratelli Hospital, Benevento, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Villari
authors.affiliation: CNR, Institute of Clinical Physiology, Pisa, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Picano
authors.affiliation: CNR, Institute of Clinical Physiology, Pisa, Italy.
authors.forename: Rosa
authors.initials: R
authors.lastname: Sicari
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002303:Cardiac Output, Low / Q000503:physiopathology; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000502:physiology*; D004176:Dipyridamole; D025401:Echocardiography, Stress; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D011446:Prospective Studies; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D004176:Dipyridamole
keywords: Coronary flow reserve; Dilated cardiomyopathy; Left bundle branch block