Arrhythmia Surgery Flashcards
What is incidence of atrial fibrillation
AF 1% in the general population
increase with age with an incidence of 0.2-0.3% at 25-35. 3-4$ at 55 to 65 and 6-9% at age 65 to 90.
most commonest arrhythmia occurring in all patients with an arrhymia.
Common causes of atrial fibrillation
Idiopathic (primary) Mitral valve disease (left atrial dilation) Ichemic heart disease Hypertension Post-cardiac surgery alcohol Thyrotoxiciosis
List risk factors for atrial fibrillation following cardiac surgery
Age withdrawal of beta blockers electrolyte imbalance hypoxia ischemia pericardial effusion infection, penumonia.
Pathophysiology of AF
AF is induced by focal areas of automaticity (mainly around the pulmonary veins) and is maintained by multiple march re-entry circuits within both atria
Treatment of parysymal AF–requires stopped the induction pathways (focal areas of automaticity) by pulmonary vein isolation
treatment of persistent AF requires elimination the maintaing pathways (macro re-rentry) using the Cox-maze procedure
What are surgical options for the treatment of AF
1) Cut and sew–surgical incisions using the lesion set described by Cox in the maze III operation
2) Radiofrequency ablation–employs an alternating current at 350kHz-1MHz to heat tissues to 70 to 80 degree for 1 mintue, creates a 3 to 6mm lesion using unipolar or bipolar devices. Transmurality is indicated by electrical conductance and impedance monitoring
3) Microwave–uses high-frequency electromagnetic radiation to induce oscillation of water molecules
4) Cryoablation, which uses nitrous oxide as a cooling agent for 2 minutes at -60 degree C to produce a transmural lesion that can be visualised as an iceball
5) Ultrasound, which uses high-frequency sound waves (2- 20 MHz) emitted by piezoelectric cyrstals to cause thermal heating and disruption of cell membranes.
6) Laster, which uses a monchromatic, phase coherent beam to cause heating and cellular destruction
What are principles of maze operation
A “maze” is created with a set of blind alleys with one entrance and one exit fro atrial electrical activation, thereby direction the electrical impulse along one specified route from the sino-atrial node to the atrioventrical node by interrupting conduction routes and re-entrant pathways.
Left atrial appendage excision is performed to reduce the area of blood stasis and potential site for thrombus
Less likely to be associated with successful outcome in patients with large left atria (>5c) or with lonstanding AF >5 year.
Describe management of atrial flutter
Aflutter is caused by a single macro re-entry circuit
Presents in variable block (2:1; 3:1;4:1) which represents an atral rate of 300 blom and a ventricular response of 150, 100, 75)
Treatment: amiodarone, calcium channel blockers, DC cardioversion, catheter ablation or surgical ablation of the flutter isthmus
Atrial flutter isthmus runs from the inferior vena caval opening along the eustachian valve and the coronary sinus, to the tricuspid valve
What is Vaughn-Williams classification of anti-arrhythmic drugs
I) Fast Sodium channel blockade 1a quinidine; procainamide;
1b lidocaine, phenytoin
1c propafenone, flecainide
II) Beta sympathetic blockade beta blockers
III) Potassium channel blockade amiodarone, sotalol
IV) Slow calcium channel blockade verapamil, diltazem, adenosine
What is incidence of AF in persons older then 65
5.9%
The absolute number of pts in AF will rise as population ages
What is Cox Maze III
This is the “cut-and-sew” technique
Study by Michael Argenziano (Coloumbia NY) JTCS 2013; 145:356-63
Right atrial lesions do not improve the efficacy of a complete left atrial lesion set in the surgical treatment of AF, but they do increase procedural morbidity
Success rates (freedom from AF or flutter at 3 months intervals)
Pulmonary vein isolation 56.7%, 56.9, 54
PVI + Mitral, + appendage 74.5%, 72%, 72%
Biatrial-extended 79%, 74, 83
Biatrial had a higher rate of pacemaker placement 16.5% vs 7.5%!
This is a weak study because it has many selection bias and it’s outcomes are not clear
List points of AF surgery
should not get heart block because you don’t ablate across the AV node
Multiple mapping studies have shown that with paroxysmal AF activation occurs from the pulmonary vein and the right atrium, indicate the left atrium set would be enough to terminate AF.
chronic AF shows a reentrant activation in the right atrium–indicating that biatrial lesion should be necessary to eliminate AF.
Right atrial size is very important in chronic AF
The CURE-AF trial: A prospective multicenter trial of irrigated radiofrequency ablation for the treatment of persistent AF during comcomitant cardiac surgery
Ralph Daminao, Jr
AATS
150 pts in 15 US centers, pts followed for 6 to 9 months and then had 24 hour holter.
All pts underwent standardized biatrial cox-max IV lesion set using irrigated RF ablation devices
total RF time was 9 min
Freedom from AF was 66% with 47% of pts off antiarrhythmic at 6-9 months
Success rate was 82% in persistent AF as opposed to 63% in permanent AF
Increased LA diameter, shorter RF ablation time, and increasing number of concomitant procedures were associated with occurrence of AF
What is WPW (wolff-parkinson white syndrome)
Short PR interval Wide QRS-delta wave Accessory pathway Free wall left atrium-type A Right atrium==anterior superior type B Atrial fibrillation can be lethal due to rapid conduction via accessory pathway--can cause VF
Catheter ablation is very successful> 99%
What are causes of VT
Idiopathic
Non-ischemic cardiomyopathy
Right ventricular dysplasia (Uhl’s anomaly)
Ischemic ventricular tachycardia
What is 4 letter code for International pacemaker
I chamber paced
II Chamber sensed
III Pacing algorith
IV Rate modulation
List different Demand (rate-inhibited) pacers
VVI and AAI
what is a VDD pacemakers
Pace maker that paces only the ventricle but sense both atrium and ventricle
List accepted indications for cardiac pacemaker in symptomatic patients with chronic conditions
Atroventricular block Complete (3rd degree) Incomplete (Second-degree) Incomplete with 2:1 or 3:1 Sinus node dysfunction sinus bradycardia sinoatrial block sinus arrest bradycardia-tachycardia syndrome
List controversial indications for cardiac pacemaker implantation
In symptomatic patients
bifascicular/trifasiciular intraventricular block
hypersensitive carotid sinus syndrome
In asymptomatic patients
Third-degree block
Mobitz II
Mobitz II atrioventricular block following myocardial infarction
congenital atrioventricular block
Sinus bradycardia < 40 with long-term necessary drug therapy
overdrive pacing for ventricular tachycardia
What is definition of first degree atrioventricular block
Prolongation of R-R interval beyond 200 milliseconds
What is second degree block
Incomplete dissociation of the atrial and ventricular rates, with increasing P-R intervals and dropped beats Mobitz I (usally AV nodal block) Mobitz II (usually in the HIS-Purkinje system)
What is 3rd degree block
complete atrioventricular dissociation
the atrial rate usually exceeding the ventricular rate
What are etiologies of AV block
Ischemic injury Idiopathic fibrosis cardiomyopathy iatrogenic injury AV node ablation Lyme disease bacterial endocarditis systemic lupus erythematosus congenital lesions
