CSC Flashcards

Which EKG leads show the heart's electrical activity in a horizontal plane?

Answer: Unipolar precordial leads

The unipolar precordial leads, labeled V1 through V6, are placed directly on the chest across the heart. These leads provide a view of the heart's electrical activity in the horizontal or transverse plane. They are crucial for detecting abnormalities such as anterior, lateral, or posterior myocardial infarctions and ventricular hypertrophy.

When the SA node fails to depolarize the atria, what is the condition known as?

Answer: Sinus pause

A sinus pause, also known as sinus arrest, occurs when the sinoatrial (SA) node, the heart's natural pacemaker, temporarily fails to generate an electrical impulse. This leads to an absence of P waves and subsequent QRS complexes on the EKG for a period. The duration of the pause can vary, and if prolonged, it may cause symptoms due to a lack of cardiac output.

A Wenckebach AV block: what is it?

Answer: Increasingly difficult AV node conduction showing a P wave not followed by a QRS complex on EKG

A Wenckebach AV block, or Mobitz Type I second-degree AV block, is characterized by a progressive lengthening of the PR interval over several consecutive beats. Eventually, an atrial impulse (P wave) fails to conduct through the AV node, resulting in a dropped QRS complex. This pattern then typically repeats, indicating increasingly difficult conduction within the AV node.

Which type of atrioventricular block doesn't affect how the heart works?

Answer: First-degree block

A first-degree AV block is characterized by a consistently prolonged PR interval (greater than 0.20 seconds) on the EKG, but every P wave is still followed by a QRS complex. This indicates a delay in conduction through the AV node or His-Purkinje system. While it signifies altered conduction, it typically does not cause symptoms or hemodynamic compromise and usually does not affect the heart's overall function.

What are a few third-degree AV block causes?

Answer: Age, digitalis intoxication, or myocardial infarction

Third-degree AV block, or complete heart block, involves a complete dissociation between atrial and ventricular electrical activity. Common causes include degenerative changes in the conduction system due to aging, toxicity from certain medications like digitalis, and damage resulting from myocardial infarction, particularly inferior wall MIs that affect the AV node's blood supply. These conditions severely impair the transmission of impulses from the atria to the ventricles.

Which kind of atrioventricular block patient in particular would be a good candidate for a pacemaker implant?

Answer: Third-degree block

Patients with third-degree (complete) AV block have a complete failure of electrical impulses to pass from the atria to the ventricles, leading to very slow and unreliable ventricular escape rhythms. This often results in severe symptoms such as syncope, dizziness, or heart failure, and carries a high risk of asystole. A permanent pacemaker is essential to provide a stable ventricular rate and prevent life-threatening bradycardia.

What condition might an EKG with tall, upright T waves or ST elevations be a very early sign of?

Answer: Transmural myocardial infarction

Tall, upright, and peaked T waves (hyperacute T waves) are often the earliest EKG sign of acute myocardial ischemia, indicating an evolving transmural myocardial infarction. These T wave changes are rapidly followed by ST segment elevation, which is a hallmark of ST-elevation myocardial infarction (STEMI). Both findings signify severe and ongoing myocardial injury.