CHAPTER 19

DISORDERS OF CARDIAC FUNCTION

CHAPTER 19

DISORDERS OF CARDIAC FUNCTION

Essentials of Pathophysiology

PRE-LECTURE QUIZ

Pericarditis represents an inflammatory process of the myocardium.

All types of angina represent an acute myocardial infarction, also known as a heart attack.

The heart extracts and uses 60% to 80% of the oxygen in blood flowing through the coronary arteries.

Atherosclerosis is by far the most common cause of coronary heart disease.

Stable atherosclerotic plaques tend to rupture more than unstable atherosclerotic plaques and lead to acute coronary syndromes, ranging from unstable angina to ST-segment elevation myocardial infarction.

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PRE-LECTURE QUIZ

 Cardiac __________ is a life-threatening, slow or rapid compression of the heart due to the accumulation of fluid, pus, or blood in the pericardial sac.

Rheumatic heart disease, a disorder that follows a group A _____________ throat infection, is of great concern because of the potential effects of chronic valvular disorders that produce permanent cardiac dysfunction and sometimes fatal heart failure years later.

__________ refers to a narrowing of the valve orifice and failure of the valve leaflets to close properly. 

Creatine kinase, myoglobin, and troponin are known as serum cardiac __________ and are useful for acute myocardial infarction determination and classification.

Coronary heart disease is a disorder of impaired __________ blood flow, usually caused by atherosclerosis.

Tamponade

Stenosis

Streptococcal

Markers

corornary

DISORDERS THAT AFFECT THE WHOLE HEART Pericardial disorders

Coronary heart disease

Myocardial diseases

These disorders can cause symptoms of both right- and left-sided heart failure

THE PERICARDIUM SURROUNDS THE HEART

PERICARDITIS

Inflammation of the pericardium causes: Pain Exudate

º Serous pericardial effusion Cardiac tamponade: rapid accumulation of

exudate compresses the heart

º Fibrous friction rub; adhesions ECG changes

PERICARDITIS (CONT.)

Inflammation of the pericardium may restrict the heart’s movement due to: Serous exudate filling the pericardial

cavity (pericardial effusion) Fibrous scar tissue making the

pericardium stick to the heart (constrictive pericarditis)

CONSEQUENCES OF

PERICARDIAL EFFUSION

fluid in pericardial cavity

restricts heart expansion

left ventricle cannot accept enough blood

decreased cardiac output

decreased blood pressure and

shock

right ventricle cannot accept enough blood

increased venous pressure; jugular

distension

QUESTION

What is the immediate treatment for severe cardiac tamponade?

a. Oxygenb. Cardiac drugsc. Surgeryd. Pericardiocentesis (removal of fluid

from the sac with a needle)

PERICARDITIS

Inflammation of the pericardium causes: Pain Exudate

º Serous pericardial effusion Cardiac tamponade: rapid accumulation of

exudate compresses the heart

º Fibrous friction rub; adhesions ECG changes

PERICARDITIS (CONT.)

Inflammation of the pericardium may restrict the heart’s movement due to: Serous exudate filling the pericardial cavity

(pericardial effusion) Fibrous scar tissue making the pericardium

stick to the heart (constrictive pericarditis)

CONSEQUENCES OF

PERICARDIAL EFFUSION

fluid in pericardial cavity

restricts heart expansion

left ventricle cannot accept enough blood

decreased cardiac output

decreased blood pressure and

shock

right ventricle cannot accept enough blood

increased venous pressure; jugular

distension

QUESTION

What is the immediate treatment for severe cardiac tamponade?

a. Oxygenb. Cardiac drugsc. Surgeryd. Pericardiocentesis(removal of fluid from the sac with a

needle)

ANSWER

d. Pericardiocentesis (removal of fluid from the sac with a needle)

Rationale: In severe cardiac tamponade, there is so much fluid in the pericardial sac compressing the heart that its function declines rapidly. The fluid must be removed quickly by inserting a needle into the pericardial space and aspirating the accumulated fluid.

PULSUS PARADOXUS

On inhaling, the right ventricle fills with extra blood

When the right ventricle is overfilled, the left ventricle is compressed and cannot accept much blood. Because the heart cannot fully expand

On the next heartbeat, the left ventricle does not send out much blood: systolic BP drops

CORONARY HEART DISEASE

Atherosclerosis blocks coronary arteries Ischemia may cause:

Angina Heart attack Cardiac arrhythmias Conduction deficits Heart failure Sudden death

Plaque/Thrombus Formation

CHRONIC ISCHEMIC HEART DISEASE

Imbalance in blood supply and the heart’s demands for oxygen Less blood

º Atherosclerosisº Vasospasmº Thrombosis

Higher oxygen demandº Stressº Exerciseº Cold

KINDS OF ANGINA

Stable angina Pain when heart’s oxygen demand

increases Variant angina

Pain when coronary arteries spasm Silent myocardial ischemia

Myocardial ischemia without pain

ACUTE CORONARY SYNDROMES

ECG changes T-wave inversion ST-segment depression or elevation Abnormal Q wave

Serum cardiac markers Proteins released from necrotic heart

cellsº Myoglobin, creatine kinase,

troponin

QUESTION

Tell whether the following statement is true or false.

Chronic ischemic heart disease is more likely to result in stable angina than acute coronary syndromes.

ANSWER

TrueRationale: Ischemic heart disease is

characterized by stable angina, which is associated with plaques that are fixed obstructions. Unstable angina is characterized by plaques with platelets stuck to them (these are likely to form a thrombus)—they cause a range of acute coronary syndromes.

ACUTE MYOCARDIAL INFARCTION

Chest pain Severe, crushing, constrictive, OR like

heartburn Sympathetic nervous system response

GI distress, nausea, vomiting Tachycardia and vasoconstriction Anxiety, restlessness, feeling of

impending doom Hypotension and shock

Weakness in arms and legs

AN ACUTE MI (AMI) LEAVES BEHIND AN AREA OF YELLOW NECROSIS

COMPLICATIONS OF AMI

Heart failure

Cardiogenic shock

Pericarditis

Thromboemboli

Rupture of the heart

Ventricular aneurysms

MALFUNCTIONING HEART MUSCLE Malfunctioning heart muscle can cause

heart failure if: Ventricles are unusually thick so there is

not a normal amount of room for blood inside them (hypertrophic cardiomyopathy)

Ventricles are too stiff to stretch (restrictive cardiomyopathy)

Ventricles are too weak to pump out the blood that is in them (MI, myocarditis, dilated cardiomyopathy)

MYOCARDIAL DISORDERS

Myocarditis Cardiomyopathies

Dilated cardiomyopathies Hypertrophic cardiomyopathies Restrictive cardiomyopathies Peripartum cardiomyopathy

HYPERTROPHIC CARDIOMYOPATHY Defects in their

contractile proteins make cells too weak

They hypertrophy to do the same amount of work as normal cells

Need more oxygen and perform less efficiently, so the person is prone to heart failure and may suffer sudden death during exertion

QUESTION

Which type of cardiomyopathy is characterized by weakened ventricles?

a. Dilated cardiomyopathyb. Hypertrophic cardiomyopathyc. Restrictive cardiomyopathyd. Peripartum cardiomyopathy

ANSWER

a. Dilated cardiomyopathyRationale: In dilated cardiomyopathy,

the ventricles are too weak to pump blood, resulting in a diminished cardiac output (CO). The other types listed are caused by thick ventricles, stiff ventricles, or LV dysfunction in late pregnancy or postpartum, respectively.

VALVULAR DISORDERS AND HEART DEFECTS

By interfering with normal blood flow, these often cause the signs and symptoms of left- or right-sided heart failure

right heart

lungs

left heart

body

THE ENDOCARDIAL STRUCTURES

The endocardial structures lining the heart can cause heart failure If the AV valves leading into the

ventricles do not work (mitral or tricuspid problems)

If the semilunar valves leading out of the ventricles do not work (aortic or pulmonary problems)

CARDIAC CYCLE

Discussion:Arrange these steps in the proper order:

– Ventricles relax – First heart sound– Start Systole – Semilunar valves open– End Diastole – AV valves close– AV valves open – Semilunar valves close– Ventricles contract – Second heart sound

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VALVE DEFECTS

Each of the four valves can be defective

Stenosis: valve will not open all the way; it is harder to force blood through it

Regurgitation: valve will not close all the way; it leaks when it should be closed

Also called valvular insufficiency

QUESTION

Tell whether the following statement is true or false.

Mitral valve regurgitation results in a diminished stroke volume.

ANSWER

TrueRationale: If the mitral valve does not

close as it should, a portion of the stroke volume (amount of blood ejected by the ventricle/beat) leaks back into the left atrium, decreasing the amount of blood that is ejected during that beat (SV).

DISCUSSION

Defects in which valves might cause: Severe dependent edema? Paroxysmal nocturnal dyspnea? Congested liver? Distended jugular veins? Productive cough with frothy sputum?

IDENTIFYING DEFECTIVE VALVES

The blood going through the valve makes a noise

These are called heart murmurs You can identify them by:

Where they are—which valve are they near?

How they sound—high- or low-pitched? When they happen—systole or diastole?

WHEN WILL YOU HEAR MURMURS?

If a valve is stenotic, you will hear a murmur of blood shooting through the narrow opening when the valve is open

If a valve is regurgitant, you will hear a murmur of blood leaking back through when the valve should be closed

LEFT-SIDED VALVULAR DISORDERS

Mitral valve disorders Mitral valve stenosis Mitral valve regurgitation Mitral valve prolapse

Aortic valve disorders Aortic valve stenosis Aortic valve regurgitation

•Aortic Valve Stenosis•Aortic valve is constricted•Difficult to pump blood from the LV•LV hypertrophy

•Mitral Regurgitation•Part of SV goes back

into the LA•Heart has to work

harder to meet body needs

•LV hypertrophy•Mitral Stenosis•Incomplete LV filling•Lower CO

•Aortic Regurgitation•Blood flows backward into the LV from the Aorta•LV Dilatation

Valvular Disorders

CONGENITAL HEART DEFECTS

Atrial septal defects

Ventricular septal defects

Endocardial cushion defects

Patent ductus arteriosus

Pulmonary stenosis

Tetralogy of Fallot

Transposition of the great vessels

Coarctation of the aorta

SHUNTS

A shunt is an opening or connection that lets blood move from one side of the circulation to the other

Most shunts occur in the heart and move blood either from the left to the right or from the right to the left

Because the left side is stronger, blood is usually pushed from the left to the right side

SHUNTS (CONT.)

Shunts are normal before birth Foramen ovale

Lets blood go from the right atrium to the left atrium to bypass the lungs

Ductus arteriosus Lets blood go from the pulmonary trunk

to the aorta to bypass the lungs Ductus venosus

Lets blood go from the visceral veins to the vena cava, bypassing the liver

LEFT-TO-RIGHT SHUNT

Less blood goes to body

More blood goes to lungs

Blood moves from left to right

right heart

lungs

left heart

body

RIGHT-TO-LEFT SHUNT

Deoxygenated blood goes to

body

Less blood goes to lungs

Blood moves from right to left

right heart

lungs

left heart

body

DISCUSSION

Show how the diagram would look for:

Patent ductus arteriosus

right heart

lungs

left heart

body

DISCUSSION

Show how the diagram would look for:

Transposition of the great vessels

lungs

body

left heart

right heart

DISCUSSION

Show how the diagram would look for:

Tetralogy of Fallot

right heart

lungs

left heart

body