Cardiac Flashcards
1
Q
Cardiovascular dysfunction can be attributed to one or more of which six mechanisms?
A
- Pump failure
- Flow obstruction
- Regurgitant flow
- Shunted flow
- Disorder of cardiac conduction
- Rupture of the hear or a major vessel
2
Q
Describe pump failure?
A
- In some conditions, the myocardium contracts weakly during systole and there is inadequate cardiac output. Conversely, myocardium may relax insufficiently during diastole to permit adequate ventricular filing.
- Congestive heart failure occurs when the heart is unable to pump at a rate sufficient to meet the metabolic demands of the tissues or can do so only at elevated filling pressure. It is common end stage of many forms of chronic heart disease, often developing insidiously from cumulative effects of chronic work overload (e.g in valve disease or HTN) or ischemic heart disease (ex. following myocardial infarction with heart damage)
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Heart failure can result from progressive deterioration of myocardial contractile function (systolic heart failure)
- reflected as a decreased in ejection fraction (EF, the percentage of blood volume ejected from the ventricle during systole; normal is approx 45-65%)
- reduction in EF can occur with ischemic injury, inadequate adaptation to pressure or volume overload due to hypertension or vavular disease or ventricular dilation
- Heart failure can also result from an inability of the heart chamber to expand and fill sufficiently during diastole (diastolic heart failure)
- Ex. Due to left ventricular hypertrophy, myocardial fibrosis, constrictive pericarditis, or amyloid deposition. No reduced EF. Positive Inoropic agents of no value. Harder to treat
3
Q
Define flow obstruction
A
- Lesion can obstruct blood flow through a vessel (ex. atherosclerotic plaque) or prevent valve opening or otherwise cause increased ventricular chamber pressure (ex. aortic valvular stenosis, systemic hypertension, or aortic coarctation). In the case of a valvular blockage, the increased pressure overload the chamber that pumps against the obstruction
- Insertion of balloon catheter expands vascular lumen & bracing stent left behind to keep it open
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4
Q
Define regurgitant flow?
A
- A portion of the output from each contraction flows backward through an incompetent valve, adding a volume overload to the affected atria or ventricles (ex. left ventricle in aortic regurgitation; left atrium and left ventricle in mitral regurgitation
- Pt with aortic regurgitation have widened pulse pressure
- REMINDER: The numeric difference between your systolic and diastolic blood pressure is called your pulse pressure.
- Ex. if your resting blood pressure is 120/80 mm of mercury (mm Hg), your pulse pressure is 40. If it becomes 150/60, the pulse pressure is 90
- This wide swing can result in CRA pressure dipping below IOP, resulting in spontaenous pulsation of the central retinal ARTERY
5
Q
Define Shunted flow
A
- Blood can be diverted from one part of the heart to the another (ex. from the left ventricle to the right ventricle), trhough defects can be congenital or acquired (ex. following myocardial infarction
- Shunted flow can also occur between blood vessels, as in patent ductus arteriosus (PDA) is a blood vessel. The ductus is a blood vessel connecting the pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus’s fluid-filled non-functioning lungs. Or between heart chamber in atrial septal defects (formaen ovale shunts blood in utero from right atrium to left atrium, by-passing the non-functioning lungs)
6
Q
Disorder of cardiac conduction
A
- Conduction defects or arrhythmias due to uncoordinated generation or transmission of impulses (ex. atrial or ventricular fibrillation) lead to non-uniform and inefficient myocardial contractions, and may in fact be lethal
- Purkinje fibers are modified cardiac muscle cells that are at risk for ischemic injuyr just like the myocardium. Heart muscle is spontaneously contractile. It takes non-ischemic, viable purkinje fibers to coordinate and set the rate of contractions
- Remember that the heart can be beating very rapidly, but if the beats are not coordinated (atrium first & ventricle second) no blood is moving - and if no blood is moving - bye bye!
7
Q
Describe rupture of the heart or major vessel
A
Ex. Gunshot to left ventricle or aortic dissection & rupture
- There is cataclysmic exsanguination, either into body cavities or externally
8
Q
What occurs if systemic peripheral resistance is increased? (Hypertension/Atherosclerosis)
A
- Left sided hypertrophy: the heart has to work harder to move blood
- Right Sided hypertrophy: if there is lung disease that inhibits blood flow through the lung, the right side of the heart has to work harder
9
Q
Left sided heart failure is most often cause by what?
A
- Ischemic heart disease
- HTN
- Aortic & mitral valvular diseases
- Aortic and mitral valvular diseases
- Primary myocardial diseases
10
Q
The clinical and morphologic effects of left-sided heart failure are consequences of…?
A
- passive congestion (blood backing up in the pulmonary circulation)
- Stasis of blood in the left side chambers
- inadequate perfusion of downstream tissues, leading to organ dysfunction
11
Q
What does this image show?
A
- Left hypertrophy
- OS is thicker, but this is ALOT thicker
12
Q
What happens if the left side of the heart loses its ability to hypertrophy anymore?
A
- It begins to fail in moving blood from the left side of the heart to the body
- Blood backs up in the lungs causing pulmonary edema
- Because this blood is backed up in the lungs, less returns to the heart to become available to organs served by aorta.
- These organs can suffer diminished flow/O2, ending up ischemic
13
Q
Right sided heart failure is most commonly caused by what?
A
- Caused by left side heart failure
- increase in pressure in pulmonary circulation from left side of the heart.
- Consequently, the causes of right sided heart fialure include all those that induce left-sided heart failure
14
Q
When does Isolated right sided heart failure occur?
A
- Isolated right sided heart failure is infrequent and typically occur in pt with one of a variety of disorders affecting the lungs; hence it is often referred to as cor pulmonale
- Right sided failure will leave excess fluid in body tissue creating “dependent edema” and can create hemorraghic ischemia in body organs
15
Q
What does this image show?
A
- Pitting edema that ocucrs with right sided heart failure
17
Q
Describe Normal ECG
A
- SA node = p-wave
- PR interval is delay between atrial contraction, and ventricular contraction
- AV node fires, conducting down right & left bundle branches (QRS complex)
- T is repolarization of ventricle
- 60-100 beats/min (bradycardia <60 vs tachycardia >100
- Regular - meaning R to R time interval essentially the same across many beats
- P wave present
- PR intervals falls within one LARGE box on ECG
- QRS interval falls withinless than 3 small boxes
18
Q
What are the signs & symptoms of atrioventricular (AV) block?
A
- First-degree AV block: Generally not associated with any sx; it is usually an incidental finding on electrocardiography
- Second degree AV block: usually asymptomatic, but in some pt, sensed irregularaities of the heartbeat, pre-syncope, or syncope may occur; may manifest on physical examination as bradycardia, and/or irregularity of heart rate
- Third-degree AV block: Frequently associated with sx such as fatigue, dizziness, light-headedness, presyncope, and syncope; associated with profound bradycardia unless the site of the block is located in the proximal portion of the atrioventricular node (AVN)
19
Q
Describe AV heartblock 1st degree
A
- Delay between atrial & ventricular contraction
- 1st degree AV block - extended (>5 blocks) but consistently longer & still regular
20
Q
Describe Atrioventricular Heart Block 2nd Degree? What are the two types?
A
- Again, delayed between A and V contraction
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Two types
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Wenkebach (Mobitz 1)
- Each PR interval longer than the last for 2-4 beats and then a missed beat
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Mobitz 2
- Each extended PR interval about the same length but then a missed beat. Like a 1st degree but with dropped beats
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Wenkebach (Mobitz 1)
