Arrhythmias

Question 1

EKG features of sinus rhythm

Answer 1

a normal P wave (atrial depolarization), PR interval (resistance to conduction at the AV node), QRS complex (ventricular depolarization), and a T wave (ventricular repolarization).
o Normal sinus rate in adults is 60-100 bpm.
o Normal PR interval is 0.12-0.20 seconds.
o Widening of the QRS, preceded by a normal P wave and a normal PR interval→rhythm is still sinus.
o Rate and regularity of rhythm may vary slightly with respiration.

Question 2

EKG features of atrial rhythm

Answer 2

rhythms originating in the atria.

Question 3

EKG features of junctional (nodal) rhythm

Answer 3

Regular, narrow (normal) QRS complex with no antecedent P waves.
o The region surrounding the AV node is often termed the “junction” and rhythms originating there are called junctional rhythms. They may be either slow or fast. They are a regular rhythm usually with narrow QRS complexes. P waves are often not seen because they are buried within the QRS complex or they may occur very shortly before or after the QRS. They are often inverted because they are conducted upward from the AV node rather than downward from the SA node.

Question 4

EKG features of ventricular rhythms

Answer 4

rhythms originating in the ventricle

Question 5

Sinus tachycardia:

Answer 5

regular, fast heart rate (>100 bpm). Commonly occurs during exercise or emotional stress. No treatment is generally needed, but in patients with coronary artery disease the increased cardiac oxygen demand may precipitate angina. Sinus tachycardia is associated with hyperthyroidism. If treatment is needed, a beta-blocker is usually effective.

Question 6

Sinus bradycardia:

Answer 6

regular, slow heart rate (<60 bpm). Common in normal individuals, especially athletes and requires no treatment. Sinus bradycardia may produce syncope during intense vagal activation as in fainting for which atropine is effective. Often occurs with small inferior wall infarctions that increase vagal tone. Can cause syncope, lightheadedness or fatigue in elderly patients with age-related dysfunction→sick sinus syndrome. Treatment may require placement of an electronic pacemaker.

Question 7

First degree A-V block:

Answer 7

PR interval prolonged, increased junctional delay.
 Causes: drug-induced (beta-blockers, some calcium blockers, digitalis), conduction system disease.
 EKG features: PR interval is greater than 0.2 seconds (one large block on the EKG).
 This is a benign condition that can proceed to more serious types of block

Question 8

Second degree A-V block:

Answer 8

Some P waves conduct and some do not.
 Causes: conduction system disease, high vagal tone, excessive effects of drugs.
 EKG features: Some P waves conduct normally to ventricles but others do not. Patterns vary.
 If the rate is too slow to slow to support cardiac output adequately, syncope or confusion may occur requiring a pacemaker.

Question 9

Third degree A-V block:

Answer 9

Both Ps and QRSs show regular rhythm, but they are at different rates.
 Causes: av node or junctional failure with aging, infarct or disruption during cardiac surgery—rarely caused by drugs.
 EKG features: Both Ps and QRSs show regular rhythm, but they are at different rates. With P rate > QRS rate.
 May cause syncope or sudden death. Usually requires a pacemaker.

Question 10

Atrial fibrillation:

Answer 10

o EKG features: irregularly irregular ventricular rhythm. No p waves.
o Causes: NI subjects, aging, post-operative, heart disease, hyperthyroidism
o Clinical manifestations: rapid heart rate (syncope, ischemia, heart failure), loss of atrial kick (heart failure), atrial thrombi (embolic stroke).
o Treatment: anticoagulation, rate control with drugs, cardioversion—electrical or drugs, ablation.

Question 11

Atrial flutter:

Answer 11

o EKG features: P waves (flutter waves) at rate of 240-320 bpm. Pulse may be regular or irregular. Ventricular rates vary widely—typically rapid if untreated.
o Complications: atrial flutter has some risk of embolic stroke due to clot in the left atrium, and may result in rapid ventricular rates that are poorly tolerated.
o Treatment: anticoagulation, rate control with drugs, cardioversion, ablation.

Question 12

Atrial tachycardia:

Answer 12

o EKG features: harrow QRS complex, P waves present, but abnormal. Heart rate may be as high as 180.
o Causes: abnormal re-entry pathway.
o Clinical manifestations: rapid heart rate, very uncomfortable and disturbing.
o Treatment: Adenosine, ablation if recurrent problem.

Question 13

Premature atrial contraction

Answer 13

o EKG features: premature beat, preceded by abnormal P wave, narrow QRS complex.
o Clinical manifestations: single-beat palpitation, most commonly noticed at rest, when low heart rates permit occurrence of premature ‘skipped beats’ and when distractions are reduced allowing awareness.
o Treatment: none. Beta-blockers if really annoying

Question 14

Premature ventricular contraction (PVC)

Answer 14

o EKG features: wide-abnormal QRS, No P-wave.
o Causes: random single, reentry arrhythmia—short path-length blocks re-entry.
o Clinical manifestations: single-beat palpitation, most commonly noticed at rest, when low heart rates permit occurrence of premature ‘skipped beats’ and when distractions are reduced allowing awareness.
o Treatment: none, beta-blockers if really annoying.

Question 15

Ventricular tachycardia

Answer 15

o EKG features: repetitive wide-abnormal QRS complexes, no p-wave,
o Causes: fibrosis, infiltrate, dilation, long path length permitting reentry.
o Clinical manifestations: very bad. Abnormal ventricular contraction
o Treatment: emergency defibrillation.

Question 16

Ventricular fibrillation

Answer 16

o EKG features: abnormal, abnormal, abnormal—all noise, no p waves, no QRS complexes, no T waves.
o Causes: can progress from ventricular tachycardia. Heart failure.
o Clinical manifestations: very bad. No ventricular contraction.
o Treatment: immediate emergency defibrillation.