Lusitropy

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Lusitropy is a term used to describe myocardial relaxation. The increase in calcium uptake by cardiomyocytes leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.

Positive

Increased catecholamine levels promote positive lusitropy, enabling the heart to relax more rapidly.

Negative

Relaxation of the heart is negatively impacted by the following factors:

1) Calcium overload - too much intracellular calcium
2) Rate of efflux of calcium through pumps - if calcium is not removed from the cell quickly enough
3) Impaired sarcoendoplasmic reticulum calcium ATPase (SERCA)- this channel in the myocyte pumps calcium from the cytoplasm of the cell into the endoplasmic reticulum.
4) TN-C binding affinity - TN-C (troponin C) is a protein that affects the myosin-actin fibers of the heart. When calcium binds, it triggers contraction of the heart. If calcium binds too easily, relaxation will become more difficult.

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Cardiovascular system, physiology: cardiovascular physiology

Heart

Volumes	Stroke volume = End-diastolic volume – End-systolic volume Cardiac output = Heart rate · Stroke volume Afterload · Preload Frank–Starling law of the heart · Cardiac function curve · Venous return curve Aortic valve area calculation · Ejection fraction · Cardiac index
Dimensions	Fractional shortening = (End-diastolic dimension – End-systolic dimension) / End-diastolic dimension
Interaction diagrams	Cardiac cycle · Wiggers diagram · Pressure volume diagram
Tropism	Chronotropic (Heart rate) · Dromotropic (Conduction velocity) · Inotropic (Contractility) · Batmotropic (Excitability) · Lusitropic (Relaxation)
Conduction system / Cardiac electrophysiology	Cardiac action potential (Atrial action potential, Ventricular action potential) · Effective refractory period · Pacemaker potential · EKG (P wave, PR interval, QRS complex, QT interval, ST segment, T wave, U wave) · Hexaxial reference system
Chamber pressure	Central venous pressure/right atrial pressure → Right ventricular pressure → Pulmonary artery pressure → Pulmonary wedge pressure/left atrial pressure → Left ventricular pressure → Aortic pressure
Other	Ventricular remodeling

Vascular system/
Hemodynamics

Blood flow	Compliance · Vascular resistance (Total peripheral resistance) · Pulse · Perfusion
Blood pressure	Pulse pressure (Systolic - Diastolic) · Mean arterial pressure Jugular venous pressure Portal venous pressure
Regulation of BP	Baroreflex · Kinin-kallikrein system · Renin-angiotensin system · Vasoconstrictors/Vasodilators · Autoregulation (Myogenic mechanism, Tubuloglomerular feedback) · Paraganglia (Aortic body, Carotid body, Glomus cell)