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