Cardiac 2 Flashcards
(14 cards)
Most of ATP in heart is used for
Contraction
Almost all ATP for heart comes from
Oxidative phosphorylation
30-40% of ATP in heart is used for
Transport (ATPase pumps)
What increases carb and decreases lipid usage by the heart?
Exercise, hypoxia, hypertrophy, failure
What increases utilization of lipids by the heart?
Fasting
Diabetes
What 4 things determine myocardial oxygen consumption?
1) heart rate (proportional)
2) wall tension * metabolically expensive ; estimated by TTI ; determined by afterload
3) stroke volume (minor influence)
4) contractility (incr contraction velocity) uses ATP! (Na/K ATPase, ATP–> cAMP, SERCA = ATPase)
Equation for tension time index
TTI = mean systolic pressure x ejection duration x heart rate
Increasing volume overload to the heart causes what kind of hypertrophy?
Eccentric hypertrophy (both radius r and thickness of heart h increase) * pathological!
Increasing pressure overload to the heart causes what kind of hypertrophy?
Concentric hypertrophy (radius stays same, thickness h increases) * good because spreads out wall tension (T=Pr/2h)
Pathologic hypertrophy (hypertension, aortic valve stenosis) increases myocyte length or width?
Width
Cardiac dilation (MI, dilated cardiomyopathy) has an increase in myosin length or width?
Length
What types of drugs are positive ionotropic drugs for the myocardium?
Beta adrenergic agonists
Cardiac glycosides
Phosphodiesterase inhibitors
What drug types are negative inotropic drugs for the myocardium?
Beta adrenergic antagonists
Calcium channel blockers
How do beta blockers work?
Decrease contractility Decreases cardiac output Decrease MAP Consume less oxygen Decrease BP (decr CO, decr level of Angiotensin II)
