Cardiac Flashcards
Cardiac output =
HR (beat/min) x Stroke volume (ml/beat) = cardiac output (ml/min)
Mediastinum
Space between lungs where heart lives
Cardiac cycle 5 steps
- Isovolumetric contraction: Ventricles are starting to contract and pressure is building. Tricuspid and mitral valves close (S1).
- Ventricular ejection: Pulmonic and aortic valves open: Blood is pushed out of the ventricles
- Isovolumetric relaxation: Pulmonic and aortic valves close (S2)
- Ventricular filling
- Atrial contraction “kick”
5 factors affecting cardiac rate
Sympathetic system
Parasympathetic system
Baroreceptors in carotids and aortic arch
Chemoreceptors
Electrolytes
Sympathetic effects on cardiac rate
Sympathetic system stimulates:
○ SA node and blood vessels to cause increased HR and vasoconstriction
○ Adrenal medulla to release epi and norepi
§ Beta1 receptors in the heart increase HR and contractility
§ Beta2 receptors cause bronchodilation and mild vasodilation in heart and lungs
§ Alpha receptors cause vasoconstriction in GI system and skin
Parasympathetic effects on cardiac rate
Parasymp system stimulates:
○ Vagal nerve stimulation causes decrease in HR by slowing SA node
§ E.g. valsalva maneuver, carotid sinus massage
Baroreceptors effect on cardiac rate
○ Sensitive to arterial pressure–increase in pressure will decrease HR and vice versa
Effects only temporary, will not mitigate chronic HTN
Chemoreceptors effect on cardiac rate
Respond to increased PaCO2, decreased PaO2 and/or decreased pH to increase cardiac activity
Electrolytes effect on cardiac rate
Affect cardiac muscle contraction
Imbalance of K+, Ca2+, or Mg2+ have strong effects on the heart
Dromotropic
something affecting conduction of the heart: positive/negative
Chronotropic
how fast/slow the heart is going
Inotropic
how strongly does the heart pump
Lusitropic
how well can the heart relax so it can fill
3 components of stroke volume
Preload
Contractility
Afterload
Preload
Volume of blood in ventricles before they contract at the end of diastole
Afterload
The pressure the ventricles are pumping against.
Systemic vascular resistance (SVR): the afterload of the left side of the heart–LV pumps against the pressure in the aorta
Right ventricle is pumping against the pressure in the lungs (PVR)
Ejection fraction
Stroke volume / End diastolic volume
The % of blood that actually gets pumped out with each beat
Defines difference between systolic and diastolic HF
Systolic HF ejection fraction
<40%
Weak ventricles cause heart to not pump well, reducing ejection fraction
Diastolic HF ejection fraction
> 50%
The heart can’t fill well due to stiff ventricle walls. Most of the blood in the ventricle gets pumped out so the ejection fraction is preserved, but it’s not a large amount of blood to begin with
Causes of systolic HF
HTN
CAD, ischemic heart disease
MI
Cardiomyopathy (blanket term for several myocardial diseases)
Valve disorders
Anemia
Causes of diastolic HF
HTN
Aging
Pericardial effusion
Pericarditis
Myocardial hypertrophy
Cardiomyopathy
Diabetes
Obesity
Onset and prone gender of systolic vs diastolic HF
Systolic: <65 males
Diastolic >65 females
Heart sounds systolic vs diastolic HF
Systolic: S3
Diastolic: S4
L sided HF backward effect
Blood starts backing up from the LV into the LA and the pulmonary veins and eventually the lungs become congested, and fluid starts coming out of the pulmonary capillaries.
L sided HF forward effect
Decreased cardiac output causes decreased tissue perfusion, which will activate RAAS in the kidneys
This causes increased BP, fluid retention, and vasoconstriction, which further increases the left ventricular preload and thus the backwards pooling of blood into the atria and pulmonary system. (the forward effect ends up contributing to the backward effect)
L sided HF backward effects CM
- Pulmonary congestion
- Dyspnea on exertion- Orthopnea
- Cough
- Paroxysmal (sudden) nocturnal dyspnea
- Cyanosis
- Basilar crackles
L sided HF forward effects CM
- Decreased perfusion>
- Fatigue- Oliguria
- Increased HR
- Faint pulses
- Restlessness, Confusion, Anxiety (poor perfusion to brain)