Arrhythmias (emphasis on Atrial fibrillation)
Definition:
Abnormality in cardiac conduction that can manifest as either change in rate or rhythm
Types and etiologies:
Bradyarrhythmia: any rhythm that results in a ventricular rate of less than 60 beats per minute.
- Sinus bradycardia: sinus rate of less than 60 beats/minute. Has normal P wave configuration consistent with origin in sinus node area. Etiology: increased vagal tone, hypothyroidism, ischemia, medication such as digoxin, beta blockers, calcium channel blockers
- AV Block
- 1st degree: conduction delay within AV node, results in prolonged PR interval on ECG of greater than 200 msec. Etiology: medication, CHF, ischemia, electrolyte abnormalities. No therapy needed.
- 2nd degree Type I (Wenckebach): progressive PR interval prolongation before a blocked or dropped beat. Etiology: medication, electrolyte abnormalities, ischemia. If symptomatic, can give atropine.
- 2nd degree Type II: abrupt AV conduction block without evidence of PR prolongation. No change in PR interval and then sudden dropped beat. Etiology: ischemia, conduction system disease. Need pacemaker.
- 3rd degree: dissociation of atrial beats and ventricular beats. Atrial impulses fail to conduct to the ventricle. And ventricle is beating on its own with a slower rate. Etiology: medication toxicity, ischemia, infiltrative disease (sarcoid, amyloid), lyme disease, Chagas disease. Need pacemaker.
Tachyarrhythmia: any rhythm with a rate in excess of 100 beats per minute
- Narrow Complex Tachycardia or Supraventricular (narrow QRS < 120 msec)
- Sinus Tachycardia. Etiology: pain, fever, hypovolemia, hypoxia, anemia, anxiety, thyroid disease; rate not greater than 220-age
- AV nodal reentrant tachycardia (AVNRT): reentrant circuit using AV node and accessory pathway, rate can be > 150.
- Atrial flutter: macro-reentry usually within right atrium (atrial rate is 300 and usually conducts 2:1 for HR = 150)
- Atrial fibrillation: see below for more
- Wide Complex Tachycardia (wide QRS > 120 msec)
- Ventricular tachycardia: monomorphic (QRS all the same size) or polymorphic Etiology: ischemia, cardiomyopathy, structurally abnormal heart, prior MI
Atrial Fibrillation
Definition:
Most common arrhythmia for which patients seek treatment. This is an irregularly irregular rhythm in which the atria depolarize chaotically and are not able to properly contract. The ventricular response to an irregular atrial beat is also irregular and sometimes rapid (ie rapid ventricular response).
Types:
Valvular atrial fibrillation: usually associated with rheumatic heart disease due to MS or MR with left atrial enlargement; *the most common type in our setting*
Isolated atrial fibrillation: secondary to another illness such has hyperthyroidism, PNA, pulmonary embolism, etc.
Lone atrial fibrillation: age < 65, no history of stroke or HTN and has absence of structural heart disease
Paroxysmal atrial fibrillation: intermittent (less than 24 hours)
Persistent atrial fibrillation: lasts > 7 days or requires cardioversion
Chronic atrial fibrillation: atrial fibrillation is the predominant rhythm
*paroxysmal, persistent, and chronic afib have the same risk of stroke
Pathophysiology:
Commonly originates from ectopic pacemakers in atria around the pulmonary veins. The loss of atrial contraction then leads to heart failure. This loss of atrial contraction also leads to stasis and clots in left atrium which further leads to thromboemboli (like stroke)
Causes or Risk factors of Atrial Fibrillation:
Acute atrial fibrillation:
Cardiac: heart failure, hypertensive crisis, ischemia, myocarditis
Pulmonary: acute pulmonary disease or hypoxia (PNA), pulmonary embolus
Metabolic: high catecholamine states (stress), infection, post-op, pheochromocytoma,
Thyrotoxicosis
Drugs: alcohol, stimulants
Chronic atrial fibrillation:
Age, hypertension, ischemia, valvular disease*, cardiomyopathy, hyperthyroidism, obesity
Signs and symptoms:
Fatigue, syncope, chest pain, palpitations. Severe symptoms include acute pulmonary edema. Many patients have no symptoms at all. Most symptoms are related to rapid ventricular rate.
Evaluation:
-ECG
-CXR
-Echocardiogram to look for valvular disease, presence of thrombus, left ventricular function
-Thyroid function tests
Treatment:
- *Rate Control (goal heart rate 60-80) – best treatment for most patients
- Beta blockers
- Calcium channel blockers
- Digoxin for heart failure patients if blood pressure is low or if severe valvular heart disease is present
- Rhythm Control – used only for severe symptomatic patients
- Amiodarone
- *Anticoagulation (reduce risk of stroke in patients with prior stroke, HTN, diabetes, TIA, older > 65, or heart failure)
- Warfarin or
- Aspirin (if monitoring of INR is not feasible) – technically an antiplatelet drug
*Thromboembolism prevention: Keeping the INR 2-3 with warfarin reduces risk of stroke by 66% in patients with above risk factors. Always monitor for risk of bleeding.
Arrythmias and Atrial Fibrillation Clinical cases
Case 1
50 yo female h/o HIV positive is admitted to ICU with bacterial pneumonia and respiratory distress. You noticed that her vital signs are blood pressure of 110/60 and her HR 140. Her pulse is regular with decreased volume. She does not have a fever. You decide to check orthostatics. Her blood pressure lying down is 110/60 and HR 140. Sitting up her blood pressure is 100/50 and HR 170.
1. Does this patient have an arrhythmia?
a. Yes, describe difference between tachy and brady arrhythmias
2. What is the definition of arrhythmia?
3. What type of arrythmia does this patient most likely have?
-sinus tachycardia
4. How would you confirm the type of arrhythmia? What test would you order?
-ECG
5. What are the causes of this type of arrhythmia?
- pain, fever, hypovolemia, hypoxia, anemia, anxiety, thyroid disease
6. How would you treat this patient’s arrhythmia?
-IV fluids, antibiotics
7. What other types of tachyarrythmias do you know about?
Case 2
35 yo male h/o HTN, diabetes and CCF due to hypertensive heart disease is admitted to the hospital for shortness of breath and acute pulmonary edema. His blood pressure is 180/100 and HR is 140 and irregular. The pulse is irregularly irregular with variable volume and a pulse rate of 100. There is no murmur.
1. What type of arrythmia does this patient most likely have?
-atrial fibrillation
2. How would you describe the difference between the patient’s heart rate and pulse?
-a pulse deficit of 40, this is why you need record both heart rate and pulse in patients with AFib
3. What other conditions can cause an irregular pulse?
-ectopic beats, heart block…
4. What other types of pulse irregularity can occur?
-regularly irregular
5. What do you expect to see on EKG?
-irregular narrow complex tachycardia consistent with atrial fibrillation with rapid ventricular response
6. What medication would you like to give this patient immediately and why?
-loop diuretics for pulmonary edema
-ACE inhibitor for afterload reduction and hypertension
-nitrates for preload reduction for heart failure
-digoxin for rate control (do not want to use beta blockers in acutely decompensated heart failure)
-LMNOP!
7. What are the basic principles of the treatment of Atrial Fibrillation?
8. What is the most likely reason that this patient has Atrial Fibrillation?
9. What are the other most common risk factors for Atrial Fibrillation in our setting?
10. What is lone atrial fibrillation? Does this patient have lone atrial fibrillation? How does management of lone atrial fibrillation differ from other cases?
You confirm the arrythmia by ECG and decide to start the patient on a medication. That afternoon, you check on the patient again and he is still in the same arrhythmia with his heart rate at 80.
7. What investigations will you order to determine the cause of the patient’s arrhythmia?
-echocardiogram
-CXR
-thyroid function tests
8. Would you consider starting this patient on any other medications?
-yes, warfarin for stroke prevention
The patient tells you that he had an episode of vomiting blood 6 months ago due to peptic ulcer disease. He had to receive 2 blood transfusions during that time. He has not had bloody stools or bloody vomiting since that time.
6. Does this change your choice of medications in this patient?
-this history increases the risk of bleeding on warfarin
-would also place the patient on a proton pump inhibitor
-avoid NSAIDs
The patient returns and his pulse is now 40 but is now regular. The heart rate is also 40.
7. What has happened to this patient and what type of arrhythmia does this patient have now?
8. What causes sinus bradycardia?
9. What other types of bradyarrythmia do you know about?
