Circulación Coronaria o cómo suplir el gasto…

Circulación Coronaria Aporte O2 Consumo O2 Capacidad de transporte O2 Regulación intrínseca Metabolitos locales Factores endoteliales Control neuronal Tensión de la pared Frecuencia cardíaca Contractilidad Efecto de las estenosis coronarias

Consumo de Oxígeno Miocárdico (ml O2/min x 100 gr) Corazón en asistolía 2 Corazón latiendo En reposo 8 En ejercicio 70

1.- Tensión de la pared ventricular Determinantes del Consumo de Oxígeno Miocárdico 1.- Tensión de la pared ventricular Ley de Laplace: h

Determinantes del Consumo de Oxígeno Miocárdico 2.- Frecuencia Cardíaca 3.- Contractilidad

Circulación Coronaria… o cómo suplir el gasto Aporte O2 Consumo O2 Capacidad de transporte O2 Regulación intrínseca Metabolitos locales Factores endoteliales Control neuronal Tensión de la pared Frecuencia cardíaca Contractilidad

Aporte de Oxígeno Miocárdico Capacidad de transporte de O2 por la sangre Concentración de Hemoglobina plasmática % saturación de la hemoglobina Flujo Coronario

Qc = Presión de perfusión Resistencia coronaria Flujo Coronario Presión diastólica Ao - Presión diastólica de VI Qc = Presión de perfusión Resistencia coronaria Compresión extrínseca Regulación intrínseca

Regulación Flujo Coronario Control tono intrínseco Metabólico Endotelial Neural Autoregulación

Regulación Flujo Coronario Metabolitos locales O2 : vasoconstricción Adenosina : vasodilatación Factores endoteliales Oxido nítrico Prostaciclina Endotelina Neural Receptores alfa : vasoconstricción Receptores beta : vasodilatación

Regulación metabólica Reserva coronaria

FISIOPATOLOGÍA DE LA ISQUEMIA Estenosis coronaria= resistencia al flujo Resistencia R = 8  L π r 4

Flujo en reposo y esfuerzo según grado de estenosis Flujo máximo Flujo en reposo

FIGURE 13-22A Effect of coronary resistance on coronary blood flow reserve. A, At rest, flow is driven by the pressure head (P) at the proximal end of the system. R1 refers to resistance offered by the large epicardial conductance vessels. R2 represents the coronary arteriolar resistance, which predominantly regulates coronary blood flow. R3 represents the resistance provided by wall tension in the subendocardium. At rest in the normal vessel, some vasoconstrictor resistance is present. In the setting of an epicardial coronary stenosis, blood flow at rest can be maintained, as coronary resistance can be lowered downstream (R2 decreased) by autoregulatory dilation. Thus, with lower resistance, flow may be maintained despite the lower pressure head at the distal end of stenosis. B, With a demand stress or with the administration of coronary arteriolar vasodilators, perfusion increases substantially in the area supplied by the normal epicardial artery as R2 decreases. However, there is blunted flow reserve in the area supplied by the stenosis because most vasodilator reserve at the R2 level has been used to maintain resting flow. (Adapted from Follansbee WP: Alternatives to leg exercise in the evaluation of patients with coronary artery disease: Functional and pharmacologic stress modalities. In Gerson MC [ed]: Cardiac Nuclear Medicine. New York, McGraw-Hill, 1997, pp 193-236.)

Stress FIGURE 13-22B Effect of coronary resistance on coronary blood flow reserve. A, At rest, flow is driven by the pressure head (P) at the proximal end of the system. R1 refers to resistance offered by the large epicardial conductance vessels. R2 represents the coronary arteriolar resistance, which predominantly regulates coronary blood flow. R3 represents the resistance provided by wall tension in the subendocardium. At rest in the normal vessel, some vasoconstrictor resistance is present. In the setting of an epicardial coronary stenosis, blood flow at rest can be maintained, as coronary resistance can be lowered downstream (R2 decreased) by autoregulatory dilation. Thus, with lower resistance, flow may be maintained despite the lower pressure head at the distal end of stenosis. B, With a demand stress or with the administration of coronary arteriolar vasodilators, perfusion increases substantially in the area supplied by the normal epicardial artery as R2 decreases. However, there is blunted flow reserve in the area supplied by the stenosis because most vasodilator reserve at the R2 level has been used to maintain resting flow. (Adapted from Follansbee WP: Alternatives to leg exercise in the evaluation of patients with coronary artery disease: Functional and pharmacologic stress modalities. In Gerson MC [ed]: Cardiac Nuclear Medicine. New York, McGraw-Hill, 1997, pp 193-236.)