anatomy & physiology of the heart
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ASESSMENT OF ASESSMENT OF CARDIOVASCULAR CARDIOVASCULAR
FUNCTIONFUNCTION
By: Esperancita A. Ferrer RN By: Esperancita A. Ferrer RN MDMD
ANATOMY OF THE HEART
Hollow muscular organ located in the MEDIASTINUM
Weight 300 g (10.6 oz)TERMS:SYSTOLE: period of ventricular
contraction resulting in ejection of blood from the ventricles into the pulmonary artery and aorta
DIASTOLE: period of ventricular relaxation resulting in ventricular fillingHeart beats 60 - 80 bpmVentricle ejects 70 mL of blood per beat
and has an output of approximately 5 L/min
LAYERS OF THE HEARTLAYERS OF THE HEARTENDOCARDIUM - inner layerMYOCARDIUM - middle layerEPICARDIUM - exterior layer
PERICARDIUM - a thin, fibrous sac
VISCERAL PERICARDIUMPARIETAL PERICARDIUM space between these 2 layers (PERICARDIAL SPACE) 30 mL of fluid
Coronary Arteries
PHYSIOLOGY OF THE HEART
CONDUCTION SYSTEMGenerate and coordinate the transmission
of electrical impulses to the myocardial cells atrioventricular contraction
CHARACTERISTICS:Automaticity: ability to initiate an
electrical impulseExcitability: ability to respond to an
electrical impulseConductivity: ability to transmit an
electrical impulse from one cell to another
SA Node
Pacemaker
of the heart
lies at junction of the right atrium superior vena cava
Impulse:60-100/min
electrical stimulation
contractioncontraction of the atriaatria
AV Node lies at the base of the interatrial septum
Impulse:40-60/min
-Coordinates
electrical
impulses
from atria to
Ventricle
-delay in AVdelay in AV
conductionconduction
Bundle of Bundle of HisHis
courses anteriorly courses anteriorly membranous membranous interventricular interventricular septumseptum
Impulse:30-40/min
Transmits Transmits impulses toimpulses to largest chamber largest chamber of the heart of the heart ((ventricleventricle))
Purkinje Purkinje FibersFibers
extends throughout extends throughout the endocardium of the endocardium of the right & left the right & left ventriclesventricles
Impulse:30-40/min
Impulse reaches Impulse reaches terminal point terminal point resulting to resulting to stimulation of stimulation of myocardial cellsmyocardial cells
ventricularventricular
contractioncontraction
Physiology of Cardiac Conduction
Cardiac electrical activity is the result of the movement of ions (charged particles such as Na, K, Ca) across the cell membrane.
CARDIAC ACTION POTENTIALCARDIAC ACTION POTENTIALelectrical changes recorded within a single cell
DEPOLARIZATIONDEPOLARIZATION electrical activation of a cell caused by the
influx of Na into the cell while K exits the cell
REPOLARIZATION REPOLARIZATION return of the cell to resting state, caused by
reentry of K into the cell while Na exits the cell
Cardiac Hemodynamics
CARDIAC CYCLE
An important determinant of blood flow in the cardiovascular system is the principle that fluid flows from a region of higher pressure to one of lower pressure.
The pressures responsible for blood flow in the normal circulation are generated during systole and diastole.
ATRIOVENTRICULAR VALVES: AVVATRIOVENTRICULAR VALVES: AVVSeparate atrium & ventriclesSeparate atrium & ventriclesTricuspid Valve & Mitral ValveTricuspid Valve & Mitral Valve
SEMILUNAR VALVES: SLVSEMILUNAR VALVES: SLVThe valve between right ventricle & pulmonary artery- The valve between right ventricle & pulmonary artery-
Pulmonic ValvePulmonic ValveThe valve between left ventricle & the aorta- Aortic The valve between left ventricle & the aorta- Aortic
ValveValve
SYSTOLESYSTOLE AVV closeAVV close DIASTOLEDIASTOLE AVV open AVV openSLVSLV openopen SLV SLV closecloseS1S1 S2 S2lublub dub dub
Key mediators in Blood Key mediators in Blood Pressure & Cardiac OutputPressure & Cardiac Output
ContractilityContractility & Preload & Preload && Afterload Afterload
Heart Rate Heart Rate (HR)(HR) xx Stroke Volume Stroke Volume (SV)(SV)
Cardiac Output Cardiac Output (CO)(CO) x Total Peripheral x Total Peripheral Resistance Resistance (TPR)(TPR)
Blood Pressure Blood Pressure (BP)(BP)
CONTRACTILITY:CONTRACTILITY: force of ventricular contraction force of ventricular contraction
PRELOAD:PRELOAD: the amount of myocardial stretch just the amount of myocardial stretch just before systole caused by pressure created by before systole caused by pressure created by volume of the blood within the ventriclevolume of the blood within the ventricle
AFTERLOAD:AFTERLOAD: the amount of resistance to the the amount of resistance to the ejection of blood from the ventricleejection of blood from the ventricle
STROKE VOLUME:STROKE VOLUME: amount of blood pumped out of amount of blood pumped out of the ventricle w/ each contraction (70ml)the ventricle w/ each contraction (70ml)
HEART RATE:HEART RATE: number of beats made by the heart number of beats made by the heart in 1 minutein 1 minute
CARDIAC OUTPUT: CARDIAC OUTPUT: total amount of blood pumped total amount of blood pumped out of the blood in 1 minute (5-6L)out of the blood in 1 minute (5-6L)
TOTAL PERIPHERAL RESISTANCE:TOTAL PERIPHERAL RESISTANCE: resistance resistance to left ventricular ejectionto left ventricular ejection
BLOOD PRESSURE:BLOOD PRESSURE: pressure exerted on the pressure exerted on the walls of the arteries during ventricular systole & walls of the arteries during ventricular systole & diastolediastole
expressed as a ratio of the systolic pressure expressed as a ratio of the systolic pressure over the diastolic pressureover the diastolic pressure
SYSTOLE:SYSTOLE: period of ventricular contraction period of ventricular contraction resulting in ejection of blood from the ventricles resulting in ejection of blood from the ventricles into the pulmonary artery & aortainto the pulmonary artery & aorta
DIASTOLE:DIASTOLE: period of ventricular relaxation period of ventricular relaxation resulting in ventricular fillingresulting in ventricular filling
CONTROL OF HEART RATECONTROL OF HEART RATE
Changes in heart rate are accomplished by reflex controls mediated by the:
1. Autonomic nervous system ANS
SNS ↑ HR PNS ↓ HR
2. Catecholamines
3. Thyroid hormone
4. Baroreceptor activity
HYPERTENSION
↓
Baroreceptors ↑rate of discharge
↓
impulses to medulla
↓
initiates PNS activity
↓
↓ HR ↓ BP
HYPOTENSION
↓
Less baroreceptor stimulation
↓
↓ PNS activity
↓
Initiatiate SNS activity
↓
↑ HR ↑ BP
CONTROL OF STROKE VOLUME3 FACTORS: I. Preload
degree of stretch of cardiac muscle fibers at the end of diastole - filling volume in the ventricles is the highest and the degree of stretch on the muscle fibers is the greatest
Frank-Starling Law of the heartFrank-Starling Law of the heart – – stretching stretching of the myocardial fibers during diastole of the myocardial fibers during diastole ↑↑the the force of contraction during systole; force of contraction during systole; resulting to resulting to ↑↑SV & SV & ↑↑COCO
II. Afterload
The amount of resistance to ejection of blood from the ventricle.
Systemic vascular resistance
resistance of systemic BP to left ventricular ejection
Pulmonary vascular resistance
resistance of the pulmonary BP to right ventricular ejection
inverse relationship between afterload and
stroke volume
Arteriolar VasoconstrictionArteriolar Vasoconstriction
↓↓
↑ ↑ Afterload ↓ SVAfterload ↓ SV
Arteriolar VasodilationArteriolar Vasodilation
↓↓
↓ ↓ Afterload ↑ SVAfterload ↑ SV
III. Contractilityforce of ventricular contractionforce of ventricular contraction
Contractility is enhanced by:1. catecholamines 2. sympathetic neuronal activity 3. medications (eg, digoxin, intravenous
dopamine or dobutamine)Contractility is depressed by: 1. hypoxemia2. acidosis3. medications (eg, beta-adrenergic blocking
agents)
↑ ↑ Preload ↑ Contractility ↓ AfterloadPreload ↑ Contractility ↓ Afterload
↑ ↑ Stroke VolumeStroke Volume
EJECTION FRACTIONpercentage of the end-diastolic volume that
is ejected with each strokeused as an index of myocardial contractility
AEF 01-23-09
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