Cardio Disease States

• Increased SA node stimulation occurs when sympathetic stimulation: more funny current which prompts more depolarization, at a rate that is mismatched with the other parts of the conduction system
• Decreases SA node stimulation when less sympathetic stimulation: Cholinergic stimulation through the vagus nerve acts on the SA node reduce the probability of pacemaker channels being open decreasing rate of depolarization and slowing HR
• Ectopic beats are beats that occur outside of the normal heart cycle.
• Early depolarizations:  Changes in membrane potential in the positive direction that interrupt normal repolarization; Are more likely to develop in conditions that prolong the action potential
• Delayed depolarizations:  Most commonly occur in states of high intracellular calcium after the depolarization has happened
• A regular irregularity on the ECG where the electrical impulse finds and circulates around excitable tissue constantly creating a kind “circular” pattern when it re-enters the cardiac cycle in an improper way
• •Infective Endocarditis: infection of the endocardium of the heart, a thin internal layer (endothelium and subendothelial connective tissue) or lining membrane of the heart that also covers its valves.
• Acute Bacterial Endocarditis: aggressive attach on healthy valves
• Subacute Bacterial Endocarditis: less aggressive organisms attacking pre-damaged valves
• Host substrates for infective endocarditis can include: native valve, prosthetic valve, and IV Drug-based.
• Name the steps of infective endocarditis pathogenesis?

  Endocardial surface injury, platelet-fibrin-thrombus formation, bacterial entry into circulation, adherence into the endocardium
• What can infective endocarditis be mistaken for?

  Rheumatic fever, myocardial infarction, or pneumonia.
• What is the typical treatment for infective endocarditis?

  Antibiotics
• In PAC, the prompting factor makes the P wave come earlier than expected, including into the vicinity of the T wave.
• The PAC is non-compensatory, so the rhythm isn’t automatically reset
• In cases of PJC, the AV junction suddenly fires a premature stimulus that depolarizes the ventricles; however, the refractory period after repolarization will not be completed before the early depolarization arrives, meaning that one ventricle may contract out of sync with the other.
• Causes of PVC include hypoxia and hypokalemia.
• PVCs Have opposite polarity of typical QRS. So if normal QRS is positive, the PVC is mostly negative.
• Block: impulses are so fast that the SA node can’t function normally and the AV node becomes blocked because impulses are faster than refractory period
• 2:1 block: 2 p waves for every QRS
• If P-waves are abnormal, this is evidence of atrial tachycardia. If P-waves are not visible, this is evidence of atrial fibrillation.
• Which disease state has a saw tooth pattern on the ECG?

  Atrial flutter
• Type I Atrial Flutter is the most common, where there is a clockwise or counterclockwise circuit in the right atrium around tricuspid.
• Type II atrial flutter is the less common type, where there are other circuits present in the atria.
• The ventricular tachycardia has wide QRS complexes because it originates in ventricle before the bifurcation and propagates in myocytes rather than through His, so slower depolarization process in QRS complex
• Torsades De Pointes - A type of ventricular tachycardia that is associated with ventricular fibrillation
• If T waves are absent, this is a sign of ventricular fibrillation
•  AV Nodal Reentrant Tachycardia (ANVRT) have a reentrant circuit within the AV node with 2 paths: slow and fast.
• Slow path of AVNRT conducts slow but repolarizes fast. Fast path is the opposite.
• What is the difference between WPW and WPW syndrome?

  The pathway is not benign in the syndrome; it is able to participate in conduction.
• If the P wave is not apparent or buried in the QRS complex, it is a sign of AVRT.
• What is the difference between ortho and anto-dromic AVRT on the ECG?

  Ortho is narrow QRS while anti is wide QRS.
• Which degrees of AV block require a pacemaker?

  Third degree AV block and 2nd degree Type II.
• 1st degree AV Block: no dropped QRS complexes, 1:1 p:wrs, pr > 0.2s.
• 2nd degree Type I: pr interval lengthens until a qrs is dropped and then resets (Wenckebach)
• 2nd degree Type II: pr intervals normal, but QRS randomly dropped; disease <AV node
• 3rd degree: atria and ventricles acting independently due to complete av block; disease <AV node
• Asystole is also known as flat line.
• Left/right Bundle Bunch Blocks: Blocks into the his bundles meaning that one side isn’t contracting appropriately, and the two sides are not contracting synchronously
• Sick sinus syndrome: Periods of inappropriate bradycardia