Cardiac Dysrhythmias

CARDIAC DYSRHYTHMIAS

*A conduction disorder that results in an abnormally slow or rapid heart rate or one that doesn't go through the conduction pathway in the normal pattern.

Normal Sinus Rhythm: Moves through conduction system normally*Impulse Starts in SA node- upright P wave before QRS*Travels to AV node- 0.12 to 0.2 secs-- PR interval*Ventricles depolarize in 0.12 secs or < (QRS complex)

Common Cause: ischemic heart disease *Also: drug therapy, electrolyte imbalances, metebolic acidosis, hypothermia, & d/t degenerative age-related changes

Sinus Bradycardia: Moves through conduction systemnormally but @ abnormally slow rate= <60/bpm. *can be normal with well conditioned heart or pathologic in heart disorders. IE- ICP, hypothyroidism, digitalis toxicity.

Sinoatrial Dysrhythmias

Sinus Tachycardia: Moves through conduction systemnormally but @ abnormally fast rate= 100-150/bpm. *normal pysiologic response in the healty heart to strenuous exercies, anxiety & fear, pain, fever, hyperthryroidism, hemorrhage, shock, or hypoxemia

*Premature atrial contraction (PAC): occur when early electrical stimulation starts in area of atria (neural tissue) other than the SA node. * *PACs can occur d/t: consumption of caffeine, nicotine or other sympathetic nervous system stimulants, in response to heart disease or metabolic disorders such as hyperthyroidism.

Atrial flutter: single atrial impulse outside the SA node causes the atria to contract at very rapid rate (200–400 cxt/min). *AV node conducts only some impulses to the ventricle= ventricular rate slower than atrial rate. *ECG: atrial waves have a characteristic sawtooth pattern.

Atrial fibrillation: several areas in R atrium initiate impulses= disorganized, rapid activity. *Atria quiver instead of contract. *Ventricles respond to atrial stimulus randomly= irregular ventricular HR (may be too infrequent to maintain adequate cardiac output) *Ibutilide (Corvert): antidysrhythmic drug used to convert new-onset atrial fibrillation into sinus rhythmalso treated with elective cardioversion or dig if ventricular rate not too slow.**High risk for blood clots-- stroke--prophylactic aspirin/ anticoagulant therapy

Ventricular Dysrhythmias

Premature ventricular contraction (PVC): a ventricular contraction--occurs early & independently in the cardiac cycle before the SA node initiates an electrical impulse. No P wave precedes the wide, bizarre-looking QRS complex. If the heart rate is very slow, the ventricles can repolarize after a PVC in sufficient time to receive the atrial stimulus right when it is due.

* PVCs in certain patterns when present with acute heart injury—IE cardiac surgery, acute MI-- suggests myocardial irritability and are precursors of lethal dysrhythmias

Ventricular tachycardia: caused by a single, irritable focus in the ventricle that initiates the heartbeat. The ventricles beat very fast (150–250 beats/min), and cardiac output is decreased. *clt can have LOC & become pulseless. *sometimes self corrects but usually needs defib.

* Ventricular Fibrillation: rhythm of a dying heart.

* Transvenous pacemaker

* Transcutaneous pacemaker

* Permanent/Implanted pacemaker

* Automatic implanted cardioverter defibrillator

Reference: Timby, B.K., & Smith, N.E. (2010) Introductory Medical Surgical Nursing, (10th Ed). Philadelphia, PA: Lippincott.