Lectures 7 and - Tachycardia vs Bradycardia vs SA, AV Node Block

10 important questions on Lectures 7 and - Tachycardia vs Bradycardia vs SA, AV Node Block

Characteristics of 1st degree AV blocks

- All waves are present
- Unusually long P-R interval
- QRS complexes still associated with P waves
- Caused by high vagal tone or conduction system disease

Characteristics of 2nd degree AV blocks

- P waves not followed by QRS complexes
- QRS complexes still associated with P waves
- Caused by high vagal tone or conduction system disease

Characteristics of 3rd degree AV blocks

- P waves not followed by QRS complexes
- QRS complexes NOT associated with P waves
- Caused by conduction system disease
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What is ventricular premature contraction?

VPCs are extra, early heartbeats from the ventricles instead of the SA node, causing a skipped beat/fluttering sensation.

How do VPCs look in ECGs?

- Wide and bizarre beats that are premature
- No P waves OR P waves have random relationship with QRS

What is Patent Ductus Arteriosus?

Congenital defect where a temporary fetal blood vessel (the ductus arteriosus) fails to close after birth, allowing oxygenated blood to flow from the aorta back into the lungs. It is also called a left-to-right shunt

What happens in systole with PDA?

High aortic pressure leads to blood flowing from aorta to pulmonary artery through the PDA. Some of left ventricle stroke volume is lost to the PA, so there is volume overload in both LA and LV, and extra pressure is needed in LV to overcome this.

What happens in diastole with PDA?

Aortic pressure falls, but still higher than pulmonary artery's pressure, thus the flow through PDA continues. This causes a continuous murmur where LA and LV remain overloaded due to ongoing increased pulmonary venous returned. Right side will be okay unless there is pulmonary hypertension.

What happens to the lungs in PDA?

Increased pulmonary hydrostatic pressure, and enlarged pulmonary artery -> leads to pulmonary edema and hypoxia/hypercapnia due to decreased gas exchange

What happens to the right side of the heart during PDA?

As the right side has to compensate for the incoming blood from aorta through PDA to pulmonary artery, it has to work harder to pump out the extra blood, leading to hypertrophy and the apex shifting to the right.

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