Cardiac Pharmacology Effects on ECG Flashcards
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Read the first 7 Cardiac Pharmacology Effects on ECG flashcards as text
A patient on warfarin for atrial fibrillation has an INR of 5.0. Which ECG change is directly caused by warfarin's anticoagulation effect?
Answer: No direct ECG effect — warfarin acts on coagulation, not electrophysiology
Warfarin is an anticoagulant that affects clotting factors, not cardiac ion channels, so it produces no direct ECG changes.
Cardioversion of atrial fibrillation with ibutilide requires close ECG monitoring for at least 4 hours post-infusion primarily because of:
Answer: Risk of delayed Torsades de Pointes due to QT prolongation
Ibutilide prolongs the QT interval and Torsades de Pointes can occur up to several hours after infusion ends, requiring extended ECG monitoring.
A patient receiving IV diltiazem for rate control suddenly develops a wide-complex rhythm after prior treatment with IV verapamil. What is the most likely cause?
Answer: Additive AV nodal and negative inotropic effects causing hemodynamic collapse with aberrant conduction
Combining IV verapamil and diltiazem creates additive calcium channel blockade, causing severe bradycardia, hypotension, and potentially aberrant conduction or escape rhythms.
Digoxin's effect on the ECG in a therapeutic patient includes all of the following EXCEPT:
Answer: Prolonged QT interval
Therapeutic digoxin shortens (not prolongs) the QT interval by accelerating repolarization, along with the classic scooped ST depression.
A patient develops a 'sine wave' pattern on ECG after starting spironolactone. The most likely cause is:
Answer: Hyperkalemia causing progressive ECG changes
Spironolactone retains potassium; severe hyperkalemia produces a sine wave pattern (merged QRS-T, no P waves) representing a pre-arrest emergency.
Which vasopressor, given in septic shock, is most likely to cause new ischemic ST depression on the ECG due to increased myocardial oxygen demand?
Answer: High-dose dopamine with strong beta-1 stimulation
High-dose dopamine has potent beta-1 effects increasing heart rate and contractility, markedly increasing myocardial oxygen demand and potentially causing ischemic ST changes.
An ECG technician notes a patient on adenosine has a delta wave that disappeared after the drug's brief AV block. This finding is most consistent with:
Answer: Wolff-Parkinson-White syndrome unmasked as a concealed bypass tract
When adenosine blocks the AV node, pre-excitation via an accessory pathway becomes visible as a delta wave; its disappearance during normal conduction suggests a concealed (retrograde-only) accessory pathway was masking it.