Patho: Cardiac Intro + Arrhythmias

The more distal the pacemaker site is, the ___ the heart rate

The more distal the pacemaker site is, the ___ the heart rate

slower

What does the LAD supply?

anterior wall and septum

What artery is known as the widow maker?

LAD

What does the circumflex artery supply?

lateral LV wall

What does the RCA supply?

RV and posterior/inferior LV wall

What reduces the SA intrinsic rate to ~70 bpm?

PNS

Conduction pathway:

SA node → AV node → His bundle → bundle branches → Purkinje fibers

What lowers contractility?

inadequate O2 supply, loss of myocardial cells

What is a normal ejection fraction?

55-65%

Afterload has a ___ relationship with stroke volume

inverse

Preload has a ___ relationship with stroke volume

direct

According to the Frank-starling relationship, more stretch = ___ contraction

greater

What is the EF % to classify heart failure?

25%

How do catecholamines and inotropic drugs increase contractility?

increasing Ca++ uptake

Bradycardia is defined by a HR of ___

<60

Tachycardia is defined by a HR of ____

>100

What are the two mechanisms for bradycardia?

SA and AV Node Dysfunction

What is another name for SA node dysfunction?

Sick Sinus Syndrome

What are some signs of SSS?

sinus pause, winded, low energy, occasional junctional rhythm

What causes SA node dysfunction?

increased vagal tone, increased aged, drugs (B blocker, Ca+ channel blockers)

What are the only 2 ways conduction can enter the ventricles?

AV node and His bundle

During junctional rhythm what node is in charge?

AV node

EKG signs of AV node dysfunction

long PR interval

complete cessation of AV node activity leads to

total heart block

The SA node paces at

60-100 bpm

The AV node paces at

40-60 bpm

The His Bundle paces at

20-40 bpm

Which degree of AV block is evident when there is long AV conduction (long PR interval) but still 1:1 AV conduction?

1st degree

Which degree of AV block is evident when not all atrial impulses are conducted to the ventricles resulting in lonely P waves?

2nd degree

Which degree of AV block is evident when there is no association between atrial and ventricular activity?

3rd degree

What causes AV node dysfunction?

increasing age, increased vagal input, drugs, congenital and acquired disorder

What diseases is indicated if the PR wave gets longer and longer followed by a dropped QRS complex?

Wenkebach

What disease is indicated if a QRS complex randomly doesn’t get through?

Mobitz II

What 3 mechanisms cause tachycardia?

increased depolarization, triggered tachycardias, reentry tachycardias

Triggered tachycardias occur when a special event happens during the …

relative refractory period

Increased automaticity of the SA node leads to what type of tachycardia?

increased depolarization

What type of tachycardia is seen in some patients taking procainamide or quinidine and digoxin toxicity?

Polymorphic ventricular tachycardia (Torsade de Pointes)

What type of tachycardia can be triggered if there is severe chest impact within a very specific point of the cardiac cycle triggering V. fib?

Commotio Cordis

What is it called when the tissue repolarizes slowly leading to a long refractory period, leaving a longer window for a triggered event to happen?

Long QT syndrome

What drugs cause QT interval prolongation?

AABCDDE

antiArrhythmics, antiAnginals, antiBiotics, antiCychotics, antiDepressants, Diuretics, antiEmetics

Reentry tachycardias occur at the ___

AV node

What is the HR usually for pts with AVNRT?

~150 bpm

AVNRT is frequently caused by?

PACs

What is the most common reentry tachycardia?

WPW

What causes WPW?

accessory AV connection

If a pt has WPW what would be a giveaway on the EKG?

delta wave and short PR

Where does SVT originate from?

above the ventricles

Management of tachycardias depends on if the ___ is narrow or wide

QRS

If the QRS complex is narrow the tachycardia is stemming from what source?

Atrial

If the QRS complex is wide the tachycardia is stemming from what source?

Ventricular

What three things determine SV?

contractility, afterload, preload

60 year old male presents to the clinic lightheaded. His EKG shows long QT interval. What arrhythmia is he most susceptible to?

triggered tachycardia

What would show on the EKG of a pt in SVT?

narrow QRS complex

What area of the heart will cause a 2.3 second pause when damaged?

SA node

Pt presents to the clinic with lightheadedness and feeling dizzy. EKG shows no association between P waves and the QRS complexes. What type of heart block is this?

3rd degree AV block