Ventricular Arrhythmias Flashcards
What are the ventricular arrhythmias?
- Premature Ventricular Beats
- Ventricular Tachycardia
- Torsades de Pointes
- Ventricular Fibrillation
What are the characteristics of ventricular arrhythmias?
- Originate in ventricles below Bundle of HIS
- Occur when electrical impulses depolarize myocardium using a different pathway from normal impulses
- Can lead to significant decrease in cardiac output
What are the EKG findings for ventricular arrhythmias?
- P wave absent
- QRS wider than normal
- T wave deflection is opposite QRS deflection
Describe PVCs
- Ectopic beats originating in ventricles
- May occur alone or in clusters of two or more (couplets, triplets)
- May occur in a repeated pattern (bigeminy, trigeminy, quadrigeminy) ≥ 3 PVC’s = V Tach
- Caused by electrical irritability in ventricle
- Multiform (mutifocal) PVC’s
- Can lead to ventricular tachycardia in cardiac disease patients
- Can ↓ CO if frequent
What are the EKG findings for PVCs?
- Occur earlier than expected
- Appear wide & bizarre
- P wave absent
- T wave has deflection opposite that of QRS
- Followed by compensatory pause allowing SA node to resume normal conduction
What is R on T phenomenon? When does it occur?
PVCs may trigger more serious rhythm disturbances when PVC occurs on downslope of preceding normal T wave (R on T phenomenon)
What can the R on T phenomenon lead to?
V tach, torsades de pointe
What are the general characteristics of v tach?
- Ventricular tachycardia (VT) is defined as 3 or more consecutive PVC’s
- May originate from working ventricular myocardium and/or from the distal conduction system
What can cause v tach?
1. Frequent complication of: A. MI B. Dilated cardiomyopathy C. Hypertrophic cardiomyopathy D. Electrolyte disturbances E. Often asst with hemodynamic compromise
What is non sustained VT?
Runs of 3 or more PVC’s lasting < 30 sec and terminating spontaneously
What is sustained VT?
Lasts > 30 sec and does not terminate spontaneously
What is the rate of VT?
Ventricular rate 100-250 beats/min
Often unstable rhythm
What can VT lead to?
- May preceed V Fib
2. Due to increased myocardial irritability
What are the EKG changes in VT?
- P wave usually absent
2. QRS wide (> 0.12 sec) & bizarre
What is monomorphic VT?
- Monomorphic: ventricular activation sequence is constant, resulting in QRS complex that remains the same
A. Seen commonly with structural heart diseases
What is polymorphic VT?
- Polymorphic: QRS complex varies from beat to beat
A. Torsades de Pointes
B. Bidirectional V Tach (rare)
What is an impetus of torsades de pointes?
Starts w/long QT interval & PVC trigger
What are the EKG findings for torsades de pointes/
- Rate 150-250 beats/min
- Rhythm irregular
- QRS wide w/ changing amplitude
- QRS complexes that rotate about baseline
What can torsades de pointes turn into?
V fib
What meds can cause torsades de pointes?
Drugs that lengthen QT interval
1. Antiarrhythmic drugs
A. Procainamide, quinidine, disopyramide (Norpace)
B. Tricyclic antidepressants
C. Haloperidol (Haldol)
D. Some antibiotics and antifungals
-Erythromycin, ketoconazole (Nizoral), trimethoprim sulfa (Bactrim)
E. Phenothiazines
-Prochlorperazine (Compazine), chlorpromazine (Thorazine), promethazine (Phenergan)
What are non-med causes of torsades de pointes?
- MI
- Electrolyte abnormalities
- High dose methadone
- Cocaine
What is bidirectional V tach?
Rare - characterized by a beat-to-beat alternation of the frontal QRS axis
What can cause bidirectional V tach?
Digitalis toxicity
What are the sxs of V tach?
- Asymptomatic → sudden death
- Syncope
- Palpitations
- Lightheadeness
- Tachycardia
- Hypotension
- Tachypnea
- Pallor
- ↓ level of consciousness
What are the dx studies for V tach?
- EKG
- Labs
A. CMP
B. Hypokalemia
C. Hypomagnesemia
D. Hypocalcemia
E. Dig level
F. Troponin
G. CK MB
H. Drug screen
I. CBC
How is treatment of VT determined?
Determined by degree hemodynamic compromise & duration of arrhythmia
How is a hemodynamically unstable pt with VT treated?
Cardioversion
100 – 360 J
How is a stable pt with VT treated?
- IV isoproterenol (Isuprel)
A. Given to shorten QT interval & prevent recurrence - Lidocaine 1mg/kg IV bolus
- Amiodarone 150 mg slow IV bolus over 10 min followed by slow infusion 1mg/min over 6 h
- Mg sulfate of 1-2 g IV bolus empirically for Torsades de Pointes
- Eliminate contributing factors
When in an Implantable cardioverter-defibrillator (ICD) indicated for a VT pt?
- Spontaneous sustained VT
- Cardiac arrest not related to transient or reversible cause
- Syncope of undetermined origin w/ sustained VT
- If meds ineffective/intolerated
- Nonsustained VT w/ CAD, prior MI, LV dysfunction, inducible VF or sustained VT during electrophysiologic study
How is a VT pt with normal LV function treated?
Amiodarone + beta blocker
Define v fib?
- Chaotic pattern of electrical activity in ventricles in which electrical impulses arise from multiple foci
- No effective cardiac contraction
- No cardiac output
- Fibrillation with no recognizable P wave, QRS, T waves
What is the pneumonic for the underlying causes of v fib?
THINK H6 T5
What are the H’s for the underlying causes of v fib?
- Hypovolemia
- Hypoxia
- Hydrogen ion (acidosis)
A. Consider bicarbonate - Hyperkalemia/hypokalemia & metabolic disorders
- Hypoglycemia (accucheck)
- Hypothermia (check core temp-rectal)
What are the T’s for the underlying causes of v fib?
- Toxins (toxicology, drug levels)
- Tamponade, cardiac (cardiac ultrasound)
- Tension pneumothorax (consider needle thoracostomy)
- Thrombosis, coronary or pulmonary (consider thrombolytics)
- Trauma
What are the sxs of v fib?
- Syncope
- Unconsciousness
- Cardiac death
What is the clinical course of V fib?
- Pulse disappears
- Collapse, unconsciousness
- Agonal breaths < 5 resp/min
- Onset of reversible death
What are the dx studies for V fib?
- CMP
- Cardiac enzymes
- CBC
- ABG
- Toxicology screens
- CXR
Why is CMP checked for V fib?
Electrolyte abnormalities
K, Mg, Ca
Why are cardiac enzymes checked for V fib?
Myocardial injury
Why is CBC checked for V fib?
Contributing anemia
Why are ABGs checked for V fib?
- Acidosis
2. Hypoxemia
Why are toxicology screens and levels checked for V fib?
- Illicit drugs
2. Digoxin
What are the CXR results in V fib?
- Pulmonary edema
- Cardiomegaly
- Injury due to CPR
How is V fib treated in the emergency setting?
- CPR w/ early defibrillation (200-360 J)
A. Endotracheal intubation/ventillation
B. Defibrillation interferes w/ re-entrant arrhythmia, allowing intrinsic pacemakers to take over - Epinephrine or Vasopressin
- Consider antiarrhythmic
A. Amiodarone or Lidocaine
B. Magnesium sulfate (Torsades de Pointes) - Defibrillation w/in 3 minutes →95% successful if underlying heart is functional (AED’s)
A. Pre-existing pump failure → success rate 30% - Search for & Tx possible contributing factors (H6T5)
How is chronic V fib treated?
- Require ICD
2. Most need antiarrhythmics drugs
What is brugada syndrome?
- Presence of an atypical RBBB w/ characteristic cove-shaped ST elevation in leads V1 to V3, & absence of obvious structural Dz
A. Enhanced w/ procainamide & quinidine - Genetic disorder characterized by abnormal ECG findings & ↑ risk of sudden cardiac death
- M > F (M = F in childhood)
What is the most common cause of sudden death in young men of SE Asian descent (< 40 yr) w/out underlying cardiac Dz?
Brugada syndrome
How does brugada syndrome present?
syncope due to polymorphic ventricular tachycardia (VT)
What is the cause of death in brugada syndrome?
V fib
What is type 1 EKG pattern in Brugada syndrome?
Coved type ST elevation w/ at least 2mm J-point elevation (gradually descending ST segment followed by a negative T-wave)
What is type 2 EKG pattern in Brugada syndrome?
Saddle back pattern w/ at least 2mm J-point elevation & at least 1mm ST elevation w/ a positive or biphasic T-wave
What is type 3 EKG pattern in Brugada syndrome?
Has either type 1 or type 2 pattern w/ < 2mm J-point elevation & < 1mm ST elevation
