Electromechanical and structural alterations in the aging rabbit heart and aorta.
Aging increases the risk for arrhythmias and sudden cardiac death (SCD). We aimed at elucidating aging-related electrical, functional, and structural changes in the heart and vasculature that account for this heightened arrhythmogenic risk. Young (5-9 mo) and old (3.5-6 yr) female New Zealand White (NZW) rabbits were subjected to in vivo hemodynamic, electrophysiological, and echocardiographic studies as well as ex vivo optical mapping, high-field magnetic resonance imaging (MRI), and histochemical experiments. Aging increased aortic stiffness (baseline pulse wave velocity: young, 3.54 ± 0.36 vs. old, 4.35 ± 0.28 m/s, P < 0.002) and diastolic (end diastolic pressure-volume relations: 3.28 ± 0.5 vs. 4.95 ± 1.5 mmHg/ml, P < 0.05) and systolic (end systolic pressure-volume relations: 20.56 ± 4.2 vs. 33.14 ± 8.4 mmHg/ml, P < 0.01) myocardial elastances in old rabbits. Electrophysiological and optical mapping studies revealed age-related slowing of ventricular and His-Purkinje conduction (His-to-ventricle interval: 23 ± 2.5 vs. 31.9 ± 2.9 ms, P < 0.0001), altered conduction anisotropy, and a greater inducibility of ventricular fibrillation (VF, 3/12 vs. 7/9, P < 0.05) in old rabbits. Histochemical studies confirmed an aging-related increased fibrosis in the ventricles. MRI showed a deterioration of the free-running Purkinje fiber network in ventricular and septal walls in old hearts as well as aging-related alterations of the myofibrillar orientation and myocardial sheet structure that may account for this slowed conduction velocity. Aging leads to parallel stiffening of the aorta and the heart, including an increase in systolic stiffness and contractility and diastolic stiffness. Increasingly, anisotropic conduction velocity due to fibrosis and altered myofibrillar orientation and myocardial sheet structure may contribute to the pathogenesis of VF in old hearts. The aging rabbit model represents a useful tool for elucidating age-related changes that predispose the aging heart to arrhythmias and SCD.
Cardiovascular Research Center, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI 02903, USA.
Leroy L
LL
Cooper
Katja E
KE
Odening
Min-Sig
MS
Hwang
Leonard
L
Chaves
Lorraine
L
Schofield
Chantel A
CA
Taylor
Anthony S
AS
Gemignani
Gary F
GF
Mitchell
John R
JR
Forder
Bum-Rak
BR
Choi
Gideon
G
Koren
D000375:Aging / Q000502:physiology*; D000818:Animals; D016880:Anisotropy; D001011:Aorta / Q000502:physiology; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D001696:Biomechanical Phenomena; D004396:Coloring Agents; D003326:Coronary Circulation / Q000502:physiology; D003627:Data Interpretation, Statistical; D016757:Death, Sudden, Cardiac / Q000473:pathology; D004452:Echocardiography; D055724:Electrophysiological Phenomena; D005260:Female; D005355:Fibrosis; D006321:Heart / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D011817:Rabbits; D012039:Regional Blood Flow / Q000502:physiology; D014693:Ventricular Fibrillation / Q000503:physiopathology
D004396:Coloring Agents