Cardiac Physiology 2

Block 4

What is isovolumetric relaxation?

ventricular pressure falls below pressure in arteries, semilunar valves close producing S2

What is rapid ventricular filling?

ventricles continue to relax, pressure drops below atria causing AV valves to open and blood flows passively into ventricles

What is reduced ventricular filling (diastasis)?

as ventricles fill, the pressure gradient between atria and ventricles diminishes, slowing the rate of filling, longest phase

What contributes to S1?

closure of the mitral and tricuspid valves at the onset of isovolumetric contraction

What contributes to S2?

closure of aortic and pulmonic valves at the beginning of diastole, onset of isovolumetric relaxation

What species are gallops considered abnormal in?

small animals

What is an S3 (ventricular gallop)?

occurs in early diastole, associated with the rapid ventricular filling phase

What condition is S3 associated with?

high left atrial pressure seen in congestive heart failure

What is S4 (atrial gallop)?

late diastole and is associated with atrial contraction

What does S4 indicate?

a non-compliant or stiff ventricle that requires forceful atrial contraction

What are three primary mechanisms of heart murmurs?

increased blood flow velocity

increased stroke volume

decreased blood viscosity (thickness of blood)

What are the characteristics of a grade 1 heart murmur?

very soft, localized, heard only in a quiet room

What are the characteristics of a grade 2 heart murmur?

soft and localized but heard immediately

What are the characteristics of a grade 3 heart murmur?

low to moderate intensity, equal to S1/S2 sounds

What are the characteristics of grade 4 heart murmur?

moderate to loud intensity

What are the characteristics of a grade 5 heart murmur?

loud, accompanied by a palpable precordial vibration (thrill)

What are the characteristics of a grade 6 heart murmur?

very loud, can be heard with the stethoscope lifted off the chest wall

Where can you hear mitral valve regurgitation?

left apical side

Where can you hear aortic and pulmonary valve regurgitation?

left basilar side

Where can you hear tricuspid valve regurgitation?

right apical side

When do systolic murmurs occur?

between S1 and S2

When do diastolic murmurs occur?

between S2 and the next S1

What does the P wave represent on an ECG?

depolarization (activation) of the atria, which initiates atrial contraction

What does the PR interval represent on an ECG?

the time it takes for the electrical impulse to travel from the SA node, to the AV node and His-Purkinje system

What does the QRS complex represent on an ECG?

the rapid depolarization of the ventricles, which triggers ventricular contraction

What does the T wave represent in an ECG?

represents the repolarization (re-setting) of the ventricular myocardium

Where is the white lead of an ECG placed?

right forelimb

Where is the black lead of an ECG placed?

left forelimb

Where is the red lead of an ECG placed?

left hindlimb

Where is the green lead of an ECG placed?

right hindlimb

How do you calculate instantaneous rate?

count the number of small boxes between two consecutive R waves

25 mm/sec; Heart Rate= 1500/(# of small boxes)

50 mm/sec; Heart Rate= 3000/(# of small boxes)

How do you calculate average rate?

count the number of QRS complexes within a set time interval

50 mm/sec; Bic pen covers 3-sec interval, multiply by 20

25 mm/sec; Bic pen covers 6-sec interval, multiply by 10

What is the normal sinus rhythm for dogs?

60-150 bpm

What is the normal sinus rhythm for cats?

140-220 bpm

What is sinus arrhythmia?

“regular irregular” where the heart cyclically speeds up and slows down, often synchronized with respiration

Which species is sinus arrhythmia considered abnormal in?

cats

What is sinus tachycardia?

faster sinus rhythm

What is sinus bradycardia?

slower sinus rhythm

What is the normal vertebral heart score (VHS) for a canine?

<11.5v

What is the normal vertebral heart score for a feline?

<8.1v

On a VD view, where is the aortic arch positioned?

11am to 1pm

On a VD view where is the main pulmonary artery?

1pm

On a VD view, where is the left auricle?

2-3pm

On a VD view, where is the right ventricle?

6-9pm

On a lateral view, where is the left atrium?

between 12pm and 3pm

On a lateral view, where is the left ventricle?

forms caudoventral border from 3-6pm

On a lateral view, where is the right ventricle located?

cranioventrally from 6-9pm

On a lateral view, where is the aortic arch?

9-10am

What is B-mode in an echocardiography?

primary mode, providing a real-time 2D cross sectional images of cardiac structures

What is M-mode in an echocardiography?

1D, ideal for measuring chamber dimensions and assessing left ventricular systolic function

What is the shortening fraction measurement?

quantifies the percentage of change in the LV internal diameter between diastole and systole

What cannot be measured by an echocardiography?

myocardial contractility

What is pulsed wave doppler?

measures blood flow velocity at a specific, user-defined location

What is continuous wave doppler?

measures the peak velocity along an entire ultrasound line

What are leakage markers of myocardial integrity?

cardiac troponin I (cTnI)

What is cTnI not useful for?

general screening test for chronic heart disease in asymptomatic animals

What are functional markers of myocardial dysfunction?

natriuretic peptides (NPs)

What is the strongest diagnostic feature of NT-proBNP?

high negative predictive value

What are high frequency echocardiograms?

high resolution, low penetration (10 MHz)

What are low frequency echocardiograms?

lower resolution, higher penetration (2 MHz)

What does blue mean in a doppler flow?

away from transducer

What does red mean in a doppler flow?

towards transducer

What part of the stethoscope is good for hearing gallops (diastolic sounds)?

bell

What characterizes a functional murmur?

soft (usually < grade 3), systolic, left basilar

What does pulse magnus mean?

very strong

What does pulse parvus mean?

small or weak

What does pulse filiformis mean?

very small

What does pulse deficits mean?

pulse rate < heart rate

When should instantaneous rate be calculated?

regular rhythms

When should average rate be calculated?

irregular rhythms