Arrhythmias

Question 1

EKG features of normal 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).
• Normal sinus rate in adults is 60-100 bpm.
• Normal PR interval is 0.12-0.20 seconds.
• Widening of the QRS, preceded by a normal P wave and a normal PR interval→rhythm is still sinus.
• Rate and regularity of rhythm may vary slightly with respiration.

Question 2

Sinus tachycardia definition/common conditions

Answer 2

• 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 3

Sinus bradycardia definition/common conditions

Answer 3

• 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 an effective tx
• 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 4

Atrial rhythms definition

Answer 4

• rhythms originating in the atria
• e.g. atrial fibrillation or atrial flutter

Question 5

Junctional (nodal) rhythms definition

Answer 5

• Regular, narrow (normal) QRS complex with no antecedent P waves.
• region surrounding the AV node = “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.
• P waves that are seen often inverted because they are conducted upward from the AV node rather than downward from the SA node.

Question 6

Ventricular rhythm

Answer 6

• rhythms originating in the ventricle
• e.g. ventricular tachycardia or ventricular fibrillation

Question 7

Causes, EKG features of first-degree AV block

Answer 7

• 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

Causes, EKG features of second-degree AV block

Answer 8

• 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

Causes, EKG features of third-degree AV block

Answer 9

• 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

Causes, EKG features, clinical manifestations, and tx of atrial fibrillation

Answer 10

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

Question 11

Causes, EKG features, clinical manifestations, and tx of atrial flutter

Answer 11

• 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.
• 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.
• Treatment: anticoagulation, rate control with drugs, cardioversion, ablation.

Question 12

Causes, EKG features, clinical manifestations, and tx of ventricular tachycardia

Answer 12

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

Question 13

Causes, EKG features, clinical manifestations, and tx of ventricular fibrillation

Answer 13

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