B P7 C67 Ventricular Arrhythmias Flashcards
Ventricular arrhythmias originate in the _____. These include premature ventricular complexes (PVCs), nonsustained and sustained ventricular tachycardias (VT), and ventricular fibrillation (VF)
Ventricular myocardium or His-Purkinje system
Ventricular arrhythmias that occur in the absence of structural heart disease and a defined ion channel abnormality are referred to as _____ and are usually benign.
Idiopathic
PVCs are due to _____, producing a depolarization wavefront that propagates through the ventricles independent of activation from the atrium and AV node
Abnormal impulse formation (automaticity, triggered activity)
or
Reentry in the ventricular myocardium or Purkinje system
A PVC is characterized by the _____.
(1) Premature occurrence of an abnormal QRS complex that usually has a duration exceeding 120 msec
(2) Corresponding T wave is typically broad and in the opposite direction of the major QRS deflection
(3) Typically not preceded by a P-wave
PVCs can also fall between sinus beats without disturbing AV conduction and without producing a pause, defined as _____ PVCs
Interpolated
If PVCs are relatively late in the cardiac cycle the PVC activation wavefront may collide with a sinus wavefront that has already reached the ventricles, producing _____.
Fusion beats
The ventricular activation sequence is largely determined by the site of initial ventricular activation and hence the _____ morphology is an indication of the location of the ventricular arrhythmia origin
QRS
Those that have a dominant S wave in V1 are termed left bundle branch block (LBBB)—like and generally originate in the _____.Those with a dominant R wave in V1 are termed right bundle branch block (RBBB)—like and generally originate in the _____ in the morphologically normal heart.
Dominant S wave in V1: LBBB - RV or IVS
Dominant R wave in V1: RBBB - LV
Analysis of the frontal plane axis and precordial lead patterns further refine prediction of the likely origin. Initial depolarization of the inferior wall produces a _____ frontal plane axisaxis, and depolarization of the anterior wall produces an _____ frontal plane axis.
Exceptions occur and predicting the arrhythmia origin from the QRS morphology is less reliable when structural heart disease with scar that changes ventricular activation is present
Inferior wall: superior frontal plane axis
Anterior wall: Inferiorly directed frontal plane axis
PVCs with a single QRS morphology are referred to as _____. The presence of PVCs with different QRS morphologies is referred to as _____ and usually indicates more than one PVC focus, although variable conduction away from a single focus is also a possible cause.
Unifocal: Single QRS morphology
Multifocal or multiform: Different QRS morphologies
Frequent multifocal PVCs are more often associated with _____.
Structural heart disease
PVCs may occur in repetitive patterns. Every conducted sinus beat followed by a PVC is _____. Every two sinus beats followed by a PVC is _____.
Bigeminy: each beat ff by a PVC
Trigeminy: Every 2 sinus beats ff by a PVC
A _____ coupling interval is consistent with reentry or triggered activity as the mechanism
Fixed
_____ coupling with a common interval between PVCs suggests abnormal automaticity from a parasystolic focus that is relatively protected from ventricular activation from conducted sinus beats.
Variable
Two consecutive PVCs are referred to as a PVC _____. Three consecutive beats is a triplet
Couplet: 2 consecutive PVCs
Triplet: 3 consecutive PVCs
Nonsustained VT is defined as a run of consecutive ventricular beats persisting for ____.
3 beats to 30 seconds
VT is also characterized by its QRS morphology. _____ VT has the same QRS morphology from beat to beat, consistent with a single origin for each beat. _____ VT has a continually changing QRS morphology. The initial beats of a run of monomorphic VT may have a variable QRS morphology.
Monomorphic: Same QRS morphology from beat to beat
Polymorphic: Changing QRS morphology
PVC frequency is associated with _____ during long-term follow-up.
Mortality and heart failure
On ambulatory monitoring PVCs increase with _____.
Age
CV risk factors: HTN and smoking
The 15-year risk of heart failure increased from 19.3% for those with _____% PVCs/day to 30.8% for those who had _____% (approximately 1000 PVCs) per day at baseline.
0.01% PVCs/d = 19.3% HF risk
1% PVCs/d or 1000PVCs/d: 30.8% HF risk
Runs of VT that are _____ raise concern for risk of rapid sustained arrhythmias causing syncope or sudden death
(1) Polymorphic
(2) Faster than 220 beats/min
(3) Start near the peak of the T-wave of the preceding sinus beat
During exercise testing _____ or more PVCs/minute occur at some stage (before, during exertion, or during recovery) in fewer than 10% of patients without a history of heart disease.
7 or more
Nonsustained VT occurs in fewer than 5%,is typically _____ beats in duration or shorter, and slower than ____ beats/ minute
5 beats in duration or shorter
<200 bpm
Benign idiopathic arrhythmias often originate from the _____.
RVOT
In competitive athletes without evidence of heart disease, 7% have PVCs during exercise testing, usually fewer than ___, and these were associated with a benign prognosis in one study.
<10
PVCs can be produced by direct mechanical, electrical, or chemical stimulation of the myocardium and are often noted during _____. Management is directed at correcting the underlying illness.
Acute coronary syndromes
Myocarditis
Hypoxia
Electrolyte abnormalities, particularly hypokalemia
Palpitations are often perceived as a “thump” or strong beat from the sinus beat terminating a _____ after the PVC
Longer period of ventricular filling
_____waves may be present in the venous pulse when the atria contract during ventricular systole of the PVC.
Cannon A waves
Although the stroke volume of the PVC is often _____ to produce a palpable pulse, premature heart sounds are commonly audible. Frequent PVCs may effectively produce bradycardia.
Insufficient
Idiopathic PVCs most often originate from a single site in the _____.
RVOT/VLOT
Valve annuli
Papillary muscle
_____ PVCs are more often associated with underlying structural heart disease
Multifocal PVCs
Very rarely closely coupled PVCs that start near the ____ wave of the preceding sinus beat initiate rapid polymorphic VT/VF that causes cardiac arrest
peak of the T wave
_____ PVCs do not require therapy unless they are occurring with sufficient frequency to depress ventricular function. Symptoms often wax and wane over long periods of time and may resolve in over a third of patients.
Asymptomatic
Mild symptoms are often sufficiently managed by _____ Removal of provocative factors, such as caffeine, is reasonable.
If treatment is required, chronic administration of a _____ is a reasonable first therapy, particularly if PVCs are increased with activity or emotion.
Efficacy is relatively low, but symptoms can be improved despite lack of a major impact on PVC frequency.
Mild: Reassurance
If treatment is required: beta- blocker - first line
Others:
NDHP CCBs verapamil or diltiazem
Class IC drugs Flecainide or propafenone
Amiodarone
Catheter ablation should be considered in Idiopathic PVCs/NSVT (With no structural heart disease/Electrical heart disease) when _____.
Therapy is warranted and beta-blockers are ineffective or not desired, particularly when a single dominant PVC morphology is identified
The likelihood of successful ablation depends on whether the PVCs are present at the time of the procedure to allow localization of its origin, and whether the focus is accessible.
Success rates are greatest for the _____, and lower for _____.
Greatest: RV outflow tract
Lower: Papillary muscles and those that arise from the basal LV septum
Catheter ablation effectively reduced RV outflow tract PVCs in ___% of patients and was more effective than chronic metoprolol or propafenone therapy
81%
Treatment with the _____ increased mortality in post-infarct patients, possibly due to proarrhythmic effects.
Class IC drug flecainide
Class III drug D-sotalol
In patients with depressed ventricular function and PVCs in the background of structural heart disease , _____ is a therapeutic option, but long-term toxicities are an important consideration
Amiodarone
Catheter ablation can be considered if a dominant PVC morphology is present that can be targeted for ablation. During ____, routine attempts to suppress PVCs with antiarrhythmic medications do not improve outcome and are not warranted.
PVCs that trigger recurrent episodes of VF, may respond to _____
Acute myocardial infarction
Quinidine
Very frequent PVCs can cause _____ of ventricular function
Reversible depression
In PVC induced CMP, most have more than ____% PVCs as assessed from at least 24 hours of ambulatory recording, but PVC frequency during any 24-hour period can vary substantially and ventricular dysfunction has been seen in patients with only ___% PVCs during a single monitoring period. Multiday ECG monitoring may provide a better assessment of PVC burden.
> 15% PCVs/d - CMP
5% - ventricular dysfunction
When depressed ventricular function is encountered in a patient with frequent PVCs there are four major possibilities:
(1) cardiac contractility may be normal, but the frequent PVCs are impairing measurement of ventricular function;
(2) PVCs are depressing cardiac contractility;
(3) an underlying cardiomyopathic process is present and causing the PVCs;
(4) An underlying cardiomyopathy is present and the PVCs are further depressing ventricular function.
_____ suggest underlying cardiomyopathy in patients with PVCs
(1) Sinus QRS duration >130 msec
(2) PVC burden < 17%
(3) Substantial LV dilation
(4) Multifocal PVCs
(5) Areas of LGE on MR imaging
If PVCs are suspected to cause or contribute to cardiomyopathy, suppression of PVCs and reassessment of ventricular function is warranted. _____ are the major pharmacologic options.
Catheter ablation is recommended if there is a _____.
Beta-adrenergic blockers and amiodarone
(1) Dominant PVC morphology that can be targeted
(2) Antiarrhythmic drug therapy is ineffective, not tolerated, or not preferred for longterm therapy
Patients with very frequent PVCs and normal ventricular function warrant follow-up. Optimal risk assessment and surveillance is not defined but annual ambulatory recording and echocardiogram is reasonable for subjects with more than _____% PVCs.
15% to 20% PVCs
The ventricular rate in accelerated idioventricular rhythm is typically _____. Conduction of sinus beats to the ventricle producing fusion beats and capture beats is common
60 to 100 beats/minute, often only slightly exceeding the sinus rate, producing interference AV dissociation
Ventricular tachycardia can be due to _____.
The management and prognosis depend on the specific type of VT and underlying heart disease.
Reentry
Triggered activity
Automaticity
The mechanism in AIVR is likely _____. This arrhythmia is usually seen in patients with structural heart disease, particularly during _____. It lasts for seconds to minutes and does not usually have an important hemodynamic effect.
Automaticity
- Reperfusion of AMI
- Myocarditis
Suppressive therapy for AIVR is rarely necessary but may be needed if loss of AV synchrony and acceleration of heart rate produces _____. Accelerating the atrial rate with administration of _____ can suppress the rhythm.
Symptoms or a fall in blood pressure in a compromised patient
Atropine or atrial pacing
Monomorphic VT is a wide QRS tachycardia that has the same ____ indicating a stable ventricular depolarization sequence for each beat. The QRS duration typically exceeds _____ msec, but is occasionally shorter for VTs originating in the septum or that utilize a portion of the Purkinje system.
It is usually regular, but ___ msec variation in cycle length is not uncommon, and occasionally marked cycle length variation is encountered in the presence of antiarrhythmic medications, or at the onset and prior to spontaneous termination.
Rates can range from slower than _____ to faster than _____/min.
The same QRS configuration from beat to beat
QRS > 120 msec
Variation: 20 msec
<100 bpm to > 270 bpm
Vagotonic maneuvers or administration of adenosine may increase AV block exposing a _____, or if 1:1 VA conduction is present in VT, may cause transient _____, confirming VT.
It is important to recognize that a 1:1 relation between atrium and ventricle does not exclude VT because _____ may occur such that each QRS is followed by a retrograde p-wave.
In many cases P-waves are difficult to discern and the relation between P-waves and QRS complexes cannot be determined with certainty.
Supraventricular arrhythmia with aberration
VA dissociation
Retrograde VA conduction
AV dissociation may be evident from the presence of _____ beats
Fusion beats or capture beats
Sustained monomorphic VT is usually regular. The atrium is not involved in the tachycardia.
The presence of _____ between ventricular and atrial activity strongly favors VT over supraventricular tachycardia, the exception being _____, which is rare in adults, and some rare forms of AV nodal reentry
Dissociation
Junctional ectopic tachycardia with aberrancy
The same wide QRS morphology during sinus rhythm and the tachycardia suggests _____; this can also occur, however, in patients with _____.
SVT with aberrancy
Bundle branch reentry VT
The majority of sustained monomorphic VT associated with structural heart disease are due to _____ through regions of myocardial scar, consisting of fibrosis and surviving myocyte bundles.
Reentry
Diminished coupling between myocyte bundles and complex anatomic arrangement of the bundles contributes to slow conduction and facilitates conduction block needed for reentry.The slow conduction occurs during propagation through the scar, which is typically a small mass of myocardium that does not contribute to the surface ECG.The QRS is inscribed when the VT wavefront reaches the border of the scar and propagates across the ventricles.
The QRS configuration reflects the “exit” of the reentry circuit from the scar. Hence the location of the scar can often be inferred from the VT ____ morphology, which is then an indication of the infarct or scar location.
QRS
Cardiac imaging will often show the area of scar as a _____. Small areas of scar, however, particularly in the RV may escape detection with imaging. In the electrophysiology laboratory scars are evident as areas of _____ due to replacement of myocardium by fibrosis and abnormal electrograms.
Cardiac Imaging:
Region of LGE
Absence of perfusion
Abnormal wall motion
EPS:
Low electrogram voltage
In the presence of disease of the Purkinje system and surrounding myocardium VT can be due to reentry circuits that utilize the bundle branches or fascicles.
The VT has a QRS morphology consistent with activation of the ventricles from the Purkinje system, resembling _____. These VTs are uncommon, occurring in fewer than 10% of patients with recurrent VT referred for catheter ablation, but are important to recognize because they can mimic _____ and most are well treated with ablation.
Bundle branch block
Mimic: SVT with aberrancy
_____ is the most common form of VT from the Purkinje system.
The circulating wavefront usually propagates down the right bundle branch, through the septum and up the left bundle branch to complete the circuit. VT has a typical _____ configuration. Rarely the circuit revolves in the reverse direction giving rise to an RBBB configuration. The VT is often rapid, faster than _____/min. It is associated with disease of the Purkinje system and often with severe LV dysfunction.
Most patients have an ____ during sinus rhythm, despite the ability of the left bundle to sustain repetitive retrograde conduction during VT.
Bundle branch reentry
LBBB
> 200 bpm
IVCD or even a pattern of complete LBBB
