Cardiac Physiology

Question 1

With cardiac dysfunction, abnormalities include EF < 40%, BNP > normal, ST elevations over 2mm and angina. What are the signs of deconditioning and peripheral ischemia?

Answer 1

DECONDITIONING
-bedrest 24-48 hours leading to exaggerated HR, BP and RR with incremental ex

PERIPHERAL ISCHEMIA
-claudication with ambulation or <0.5 ABI

Question 2

What’s a rule of thumb for HR and BP increases per 1 MET activity?

Answer 2

10 bpm or 10mmhg (systolic).

Question 3

Problems with chordae tendinae result in the regurgitation of blood. What is another valve pathology that can lead to the opposite problem?

Answer 3

Valve stenosis; also increases workload by decreasing diameter.

Question 4

30 to 40% of people do not have a fully closed foramen ovale. What is the danger with this condition?

Answer 4

Blood clots can skip the lungs (pulmonary embolism) and go to the brain inducing a stroke.

Question 5

Why does a pulmonary embolism lead to systemic edema?

Answer 5

• Right side of heart doesn’t pump blood forward into lungs

- Fluid backs up and gets stuck in the rest of body because it can’t be pumped out by the heart

Question 6

The RCA supplies the right atrium and the LAD supplies most of the left ventricle. Which arteries supply most of the left atrium and right ventricle?

Answer 6

Left atrium = Left circumflex artery (L Cx)

Right ventricle = RCA

Question 7

Describe the physiology that is seen in an EKG, mainly the P wave and QRS complex.

Answer 7

P WAVE
-Atria contract at the end of ventricular diastole

QRS COMPLEX

• Ventricles need to overcome afterload (pressure existing in the pulmonary artery and aorta) that exists in the pulmonary or aortic artery, allowing the valves to open and blood to leave the ventricle
• The QRS complex is this depolarization and repolarization occurring to accomplish this task.

Question 8

What does the S1 sound observe?

Answer 8

Mitral and tricuspid valve closure (end diastole, lub).

Question 9

What does the S2 sound observe?

Answer 9

Closure of the aortic and pulmonic valves (end systole, dub).

Question 10

Venous return and sclerosis of arteries and values can influence cardiac functioning. What 3 factors affect stroke volume (avg 80ml/beat)?

Answer 10

1. Preload (tension created by end diastolic volume)
2. Afterload (pressure to pump against)
3. Contractility (frank-starling: pre-stretched tissue contracts more effectively)

CO = HR x SV

Question 11

What does an ECG measure?

Answer 11

Valve function
EF (SV/LVEDV, SV = LVEDV - LVESV)
Wall motion
Effusion
Wall thickness

Question 12

S3 and S4 heart sounds are usually indicative of pathology. What do they observe?

Answer 12

S3: occurs in heart failure
S4: sound of A-V valves opening

Question 13

Electrical impulses in the heart go from the SA node to the AV node to the left and right purinkje fiber bundle branches. Where are each located?

Answer 13

SA node (60-100 bpm): superior part of right atrium
AV node (40-60 bpm): inferior right atrium near septum

Question 14

What type of receptors are used in the heart?

Answer 14

Beta 1 adrenergic receptors (epinepherine and norepinepherine).

Question 15

In the P QRS T waveform, what does the T represent?

Answer 15

Ventricular repolarization.

Question 16

In an ECG strip, what are the time dimensions of the boxes?

Answer 16

• Each little square is 1 mm long and 0.04 sec
• Each large square is 5 mm long and 0.2 sec
• 15 boxes is 3 seconds

Question 17

With atrial fibrillation there is a quivering or twitching of atrial muscle and absent P waves. What are the implications of this?

Answer 17

Decreased diastolic filling time with increased rate and loss of atrial kick, leading to decreased cardiac output.

Question 18

Atrial flutter shows P waves in a sawtooth pattern. Implication?

Answer 18

Decreased diastolic filling time and loss of atrial kick, which leads to decreased cardiac output.

Question 19

Premature ventricular contractions occur with a prolonged QRS complex and irregular rhythm. Implications?

Answer 19

• No atrial kick and decreased diastolic filling time -> decreased stroke volume
• With increased frequency of PVCs -> decreased cardiac output
• This may indicate increased ventricular irritability can progress to VT or V fib

Question 20

With trigeminy and bigeminy, PVCs occur every third and second beat. What are the implications?

Answer 20

• Can have decreased cardiac output.

- Treat if rhythm unchanged

Question 21

What is it called when you have 2 PVCs in a row? 3?

Answer 21

Couplet, triplet.

Question 22

What qualifies ventricular tacchycardia?

Answer 22

> = 4 PVCs in a row

• decreased CO
• Don’t treat