32/33 - Arrhythmias Flashcards
Hormones & Channels
for the
SA&AV Node
ACETYLCHOLINE
Catecholamines** + **Ca++ Channels
same for chambers
Hormones & Channels
for the
Heart Chambers
R/L Ventricle + R/L Atriums
Na+** & **K+ Channels
unique to chambers
Catecholamines** + **Ca Channels
also for SA/AV nodes
What is the FUNNY CURRANT?
IF
PACEMAKER CELL
in the SA Node
creates the AUTOMATICITY for the
start of depolarization
Cardiac Conduction
P / QRS / T
- *P-Wave**
- *DEpolarization of ATRIUM**
QRS
DEpolarization of VENTRICLE
+ masks the repolarization of ATRIUM
- *T-Wave**
- *Repolarization of Ventricle**
What is the
RR-Interval?
RR Interval is:
HEART RATE
Distance between QRS PEAKS
QTc Prolongation Definition
Male + Female
Male > 470
Female > 480
How to calculate QTc from ECG?
Calculation + Quick & Dirty Method
QTc** = **Qt / √RR
Quick & Dirty method to see if prolonged QTc:
T-wave ends BEFORE the HALFWAY POINT
between the
R-R PEAKS
(sec)
Mechanisms of Arrhythmias
Enhanced Automaticity
Causes + Characteristics
Drugs: Catecholamines
Conditions: Hypoxia / HypoKalemia
Cardiac Dilation / EXERCISE
Characteristics:
Onset is UNRELATED to initiating event = PVC
Initiating beat IDENTICAL to Subsequent beats
onset is preceded by GRADUAL acceleration & termination
by gradual deceleration
Mechanisms of Arrhythmias
TRIGGERED
DAD = Delayed After Depolarization
Causes + Characteristics
- *Ca2+ Overload**
- *MI / Adrenergic Stress / DIGitalis Intoxication**
More common at:
FAST cardiac rates
Mechanisms of Arrhythmias
TRIGGERED
EAD = Early After Depolarization
Causes + Characteristics
- *PROLONGation of AP**
- *1a + 1c Drugs**
Most common when:
- *HR is SLOW**
- HypoKalemia*
Mechanisms of Arrhythmias
RE-ENTRY
Anatomical ReEntry
Causes + Characteristics
Causes:
Additional Pathway** / **Scarred Ventricle
Characteristics:
Presence of an anatomically DEFINED circuit
Heterogeneity in refractoriness among regions in circuit
SLOW conduction
Mechanisms of Arrhythmias
RE-ENTRY
Functionally Defined Re-entry
Causes + Characteristics
Causes:
- *HEART DISEASES**
- *CAD / LV dysfxn / MI**
Characteristics:
Non-excitable tissue is at the core = Refractory
DOESNT have to stay in the SAME anatomical position
HARDER to TREAT, continuously moving
Mechanisms of Arrhythmias
Enhanced Automaticity
MANAGEMENT
INHIBITION OF AUTOMATICITY
↓Slope of Phase 4
BB’s
- *Elevate Threshold Potential**
- *Na+ / Ca+** Channel Blockers
↑Max Diastolic Potential
Adenosine / Acetylcholine
↑Action Potential Duration
K+ Channel Blockers
Mechanisms of Arrhythmias
TRIGGERED
DADs
TREATMENT
Ca2+ Overload / FAST cardiac Rates
INHIBITION OF DADs
- *↓Ca2+ Influx_ > ↓_SR Load_ & ↓_Ca2+ release from SR**
- *Ca** Channel Blockers
- *↑Threshold Required** to create the Abnormal Upstroke
- *Na+** Channel Blockers (Ic)
Mechanisms of Arrhythmias
TRIGGERED
EADs
TREATMENT
Prolongation of AP 1a/1c drugs
HR IS SLOW / HypoKalemia
INHIBITION OF EADs
- *Shorten the AP duration**
- *ISOPROTERENOL** to acceleratte the HR
Mg2+
without normalization repolarization / QT
Mechanisms of Arrhythmias
ANATOMICAL REENTRY
TREATMENT
slow conduction
Anatomically Reentry
- *↑Refractory Period**
- *K+** Channel Blockers / Ca2+ Blockers (SA/AV node)
- *BetaBlockers** (Sa/AV node)
- *Adenosine** (AV nodes)
↓Conduction Velocity
Na+ Channel Blockers / Ca2+ Channel blockers
Adenosine + Beta Blockers
Mechanisms of Arrhythmias
Functionally Defined Re-entry
TREATMENT
non-excitable refractable
Functionally Defined Reentry
- *↑Refractory Period**
- *K+** Channel Blockers
- *Na+** Channel Blockers
Atrial Fibrilation
Mechanism + Origin
ALL 3
Automaticity + Triggered + Reentry
Origin:
Atria / Thoracic Veins / Pulmonary Veins / SVC / Vein of Marshall
VARIABLE
AV or VA conduction
Atrial Flutter
Mechanism + Origin
REENTRY
Origin:
RA / LA (infrequent
VARIABLE
AV or VA conduction
Ventricular Tachycardia
Mechanism + Origin
ALL 3
Automaticity + Triggered + Reentry
Origin:
Ventricles
AV Dissociation + Variable