- Contractility = the change in force generated independent of preload
- Inotropy and contractility are essential synonymous — inotropes are agents that increase contractility.
- the slope of the end-systolic pressure volume relationship (ESPVR) curve indicates the maximum rate of force development by the ventricle.
- substrate supply – glucose, fat, protein
- integrity of myofilaments
- co-ordinated depolarisation
- metabolic/electrolyte homeostasis
- functional muscle mass
- coronary blood flow (hypoxia)
- autonomic tone – sympathetic and parasympathetic
- hormones – thyroid, insulin/glucagon
Minor increases in contractility occur as an intrinsic response to:
- increased afterload (Anrep effect)
- increased heart rate (Bowditch effect, Bowditch phenomenon)
MANIPULATION IN ICU
- nutrition: substrate supply
- pacing: co-ordinated depolarisation
- electrolyte replacement
- treatment of negative inotropic conditions: acidosis, sepsis, heart failure, AMI
- avoidance of negative inotropic drugs: beta-blockers, Ca2+ channel blockers
- coronary blood flow + functional muscle mass: thrombolysis, PCI, bypass surgery; maintain DBP
- analgesia/sedation/paralysis: decrease autonomic tone, decrease O2 consumption
- inotropes: adrenaline, milrinone, noradrenaline, dobutamine, glucagon, insulin, levosemendin
- improve O2 delivery: increase FiO2, blood transfusion for severe anemia
- correct endocrine deficiencies: hydrocortisone, thyroxine replacement
References and links
- Cardiovascular Physiology Concepts — Cardiac inotropy (contractility)
- Noble MIM. An introduction to modern work on the Bowditch phenomenon. Cardiovascular Research 1988; 22(8): 586
- von Anrep G. On the part played by the suprarenals in the normal vascular reactions of the body. J Physiol. 1912 Dec 9;45(5):307-17. [PMC1512890]
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.