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not connected to specialized conducting tissue (His“Purkinje
be used to treat ventricular dysrhythmias refractory to lidocaine
and procainamide.44 system), early activation is slow, resulting in a slurring of the



41
1 Cardiovascular and respiratory disorders


Table 2.9 Preexcitation syndromes

Type EKG Dysrhythmias Clinical implications Treatment

1. PSVT with widea QRS:
Wolff“Parkinson“ Short PR < 120 ms Recurrent May be asymptomatic but
White (WPW) syndrome wide QRS > 120 ms tachydysrhythmias: with typical ECG pattern; suspect AF/flutter
14“90% WPW ¼ " frequency dysrhyth-
Type A: premature delta wave; ST-T DC cardioversion
excitation of LV directed opposite AV reentrant tachycar- mias in pregnancy (50“100 joules) or i.v. sotalol,
delta wave þ QRS
Type B: premature dia, atrial fibrillation, Associated conditions: flecainide, disopyramide,
or amiodarone (aadenosine
excitation of RV vectors or atrial flutter MVP
Most often precipitated Ebstein anomaly, contraindicated)
by premature beat balloon mitral 2. Surgical interruption of
valve þ/“
arising in atria, accessory pathway after
ventricle mitral insufficiency, epicardial mapping (when
or AV junction ASD/form fruste not pregnant)
cardiomyopathy
Fetus with WPW
predisposed to
dysrhythmias in utero
Lown Ganong Levine & PR usually short; Variety of 1. AV reentrant tachycardia
variants QRS normal; tachydysrhythmias can (PSVT) with narrow QRS:
Refractory period be life-threatening: i.v. adenosine or verapamil
normal or decreased “ Tachycardia with (Alt: digoxin, propranolol)
regular narrow QRS 2. Cryoablation of AV
“ AF with rapid node“His bundle
ventricular response
“ VT/VF
Nodoventricular þ Reentrant tachycardias Associated condition(s):
Fascioventricular Ebstein anomaly

AF ¼ atrial fibrillation; AV ¼ atrioventricular; MVP ¼ mitral valve prolapse; ASD ¼ atrial septal defect; DC ¼ direct current; i.v. ¼ intravenous;
VT ¼ ventricular tachycardia; VF ¼ ventricular fibrillation PSVT ¼ paroxysmal supraventricular tachycardia



ventricular complex (delta wave). During sinus rhythm, the conduct very quickly. The EKG will show a totally irregular ven-
ventricular complex is a fusion between the delta wave and tricular response characteristic of AF. The shape of some of the
normal QRS complex. ventricular complexes will be normal, but most ventricular com-
plexes will show delta waves. A very rapid ventricular response to
AF can lead to heart failure, shock, and an increased risk of VF.
EKG findings
Ventricular fibrillation is usually seen when the interval between
The typical EKG in WPW syndrome shows a shortened PR interval delta waves during AF is < 250 ms. The risk of VF is very low in
< 120 ms with a slurred upstroke (delta wave) and broadened QRS individuals who are asymptomatic and in those with intermittent
complex and ST-T waves directed in the opposite direction from accessory pathway conduction.
the QRS vector (see Figure 2.2). Usually the AV node recovers before the accessory pathway
after excitation. If an atrial ectopic beat arises during sinus
rhythm when the AV node has recovered but the accessory path-
Associated dysrhythmias
way has not, the resulting ventricular complex will be narrow
Approximately two-thirds of individuals with preexcitation and not have a delta wave. By the time the PAD has traversed
develop cardiac dysrhythmias during their life. The incidence of the AV junction and ventricles, the accessory pathway will have
supraventricular dysrhythmias in women with WPW syndrome recovered and be able to conduct the impulse back to the atria.
may increase during pregnancy.54 Two dysrhythmias occur with When the impulse reaches the atria, the AV junction will again
WPW syndrome: AF and, more commonly, atrioventricular reen- be able to conduct and the impulse can repeatedly circulate
trant tachycardia. between atria and ventricles, leading to an AV reentrant tachy-
When AF (350“600 impulses/min) occurs in individuals with- cardia. Similarly, a ventricular ectopic beat during sinus rhythm
out preexcitation, the AV node protects the ventricles from rapid can be conducted to the atria via the accessory pathway and
atrial activity. Individuals with WPW syndrome who develop AF initiate AV reentrant tachycardia. The EKG will show narrow
can have very fast ventricular rates, as the accessory pathway can ventricular complexes (unless there is a rate-related BBB) in



42
Chapter 2




Figure 2.2 EKG of patient with Wolff“Parkinson“White syndrome.


rapid regular succession. Unlike AF, there will be no delta waves, During AV reentrant tachycardia (orthodromic type), there
and there will be no clue from the ventricular complexes that are no delta waves and no evidence from the ventricular complex
WPW syndrome is present. This is termed orthodromic AV reen- of preexcitation. Treatment is the same whether or not there is
trant tachycardia (anterograde conduction via normal AV node preexcitation. Vagal stimulation (carotid sinus massage, Valsalva
pathway, retrograde conduction from ventricles to atria via acces- maneuver) is chosen frequently as the initial treatment for AV
sory pathway). Antidromic AV reentrant tachycardia, much less reentrant tachycardia, followed by adenosine (see Table 2.10).
common, occurs when anterograde conduction from atria to During AF associated with WPW syndrome, most of the ventri-
ventricles is over the accessory pathway and return to the atria cular complexes are broad due to presence of large delta waves.
is via the AV pathway. The ventricular complexes will be in the If the hallmark of AF (totally irregular rhythm) is ignored, the
form of large delta waves. rhythm may be mistaken for VT. Most atrial impulses are con-
ducted to the ventricles via the accessory AV pathway during
AF. Cardioversion is the simplest method for termination of AF
In pregnancy
and has been used successfully, with no adverse effects on preg-
nancy, mother, or fetus, with the exception of transient fetal
As noted earlier, pregnancy may predispose women to the devel-
dysrhythmias.56 If AF recurs frequently, cardioversion is not
opment of tachydysrhythmias. Women with known WPW syn-
appropriate and a drug that will slow conduction in the accessory
drome whose condition has been stable during the nonpregnant
state can develop dysrhythmias during pregnancy.54,55,56,57,58 It is pathway, such as sotalol, flecainide, disopyramide, or amiodar-
one, is recommended. These drugs slow the ventricular response
important to monitor the at-risk parturient sufficiently to identify
to AF and frequently restore sinus rhythm.20 Digoxin and verapa-
a tachydysrhythmia, as well as monitor the fetus to detect adverse
mil should be avoided because they may increase conduction
fetal effects from a dysrhythmia.
through the accessory pathway, increase the ventricular rate,
and precipitate VF. The risk of VF is increased when the minimum
Treatment interval between delta waves during AF is < 250 ms.20
Radiofrequency ablation of the accessory pathway should be
considered in all symptomatic individuals, especially if drug
Anesthetic implications
therapy is ineffective or cannot be tolerated, or if there is a
fast ventricular response to AF.55 Occasionally, ablation is indi- Tachydysrhythmias may develop during anesthesia in individuals
cated in an asymptomatic individual when the consequences of with known WPW and other preexcitation syndromes. Women
developing a serious dysrhythmia might jeopardize their safety presenting for anesthesia with an established tachycardia are, of
or that of others by nature of their occupation. The success course, best treated by first correcting the dysrhythmia. In gen-
rate for radiofrequency ablation procedures is high and the eral, agents and techniques likely to cause undue tachycardia and
risks are low. circulatory disturbance should be avoided.



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Table 2.10 Treatment of WPW dysrhythmias Table 2.11 LQTS: classification and etiology

Atrioventricular reentrant Congenital syndromes Jervell, Lange-Nielsen syndrome
tachycardia Atrial fibrillation (AF) (autosomal recessive)
Romano-Ward syndrome
ECG: broad ventricular complexes
(autosomal dominant)
(large delta waves) þ totally
Acquired
irregular rhythm (can be mistaken
Electrolyte abnormalities Hypokalemia, hypomagnesemia,
for VT)
Malnutrition or liquid-protein hypocalcemia
Risk of VF during AF when < 250 ms
diet
between delta waves
Antidysrhythmics: a
Drugs:
Treatment: Treatment:
Cardiac Class Ia agents: quinidine,
1. Vagal stimulation 1. Cardioversion: simplest, safest
procainamide, disopyramide
2. Drugs: adenosine, method to terminate AF (unless
Class Ic agents: flecainide,
verapamil frequently recurrent)
encainide, indecainide, lidocaine
3. DC cardioversion (with 2. Drugs: ibutilide (acute conversion
Class III agents: amiodarone, sotalol
sedation or GA) of AF, FDA approved), amiodarone,
Coronary vasodilator: prenylamine
4. Pacing (overdrive or sotalol, flecainide (slow conduction
Anesthetic Thiopental, succinylcholine,
programmed stimulation) in the accessory pathway)
epinephrine, norepinephrine
Avoid AV nodal blocking drugs
Psychotropic Phenothiazines, tricyclics, tetracyclic
(digoxin, verapamil, beta-blockers)
drugs
which # refractory period in
Miscellaneous Organophosphate insecticides, other
accessory pathway," ventricular
Central nervous or Intracranial, subarachnoid
rate and may precipitate VF
autonomic system injury hemorrhage
Prevention: Prevention:
Acute cerebral thrombosis
1. Drugs: amiodarone, sotalol, 1. Ablation of accessory pathway
Cardiac diseases Bradydysrhythmias:
flecainide Consider in all symptomatic
sick sinus syndrome, high-grade
2. Ablation of accessory patients (success-rates high,
AV block
risks low)22
pathway
structural heart disease
Consider in all symp-
ischemic heart disease, mitral
tomatic patients (success-
valve prolapse
rates high, risks low)22
cardiomyopathy, myocarditis,
WPW ¼ Wolff“Parkinson“White; DC ¼ direct current; GA ¼ general ischemia
anesthesia; VT ¼ ventricular tachycardia; VF ¼ ventricular fibrillation Metabolic abnormalities Hypothyroidism, hypothermia

a
Vaughan Williams classification of antidysrhythmic drugs
LQTS ¼ Long QT syndrome; AV ¼ atrioventricular
Avoiding aortocaval compression is important. The effects
of such an obvious insult to cardiac output, especially if the
woman is already compromised by a tachydysrhythmia, can be
disastrous. TdP associated with QT prolongation appears related to est-
rogen levels and is more frequent in menstruating women.
Women appear to be especially susceptible to QT prolongation
Long QT syndrome
from drugs and the incidence of TdP associated with medications
Long QT syndrome (LQTS) refers to a heterogeneous group (e.g. quinidine, class III antidysrhythmics, tricyclic antidepres-
sants) appears higher in women.59,60 The degree of QT prolonga-
of disorders (see Table 2.11) that have in common a prolonged
QT interval on EKG and a propensity to a particular type of tion does not seem to have any prognostic value.
VT called Torsade de Pointes (TdP). Cardiac output and BP tend Long QT syndrome is now understood to be a collection of
to fall dramatically with resultant syncope. Most tachydysrhyth- genetically distinct dysrhythmogenic cardiovascular disorders
mic episodes stop spontaneously with return of consciousness, resulting from mutations in the genes encoding the ion channels
but some may degenerate into VF and result in sudden cardiac responsible for three of the fundamental ionic currents in the
cardiac action potential.61 More than 35 mutations in 4 cardiac
death. Ventricular dysrhythmias and symptoms are frequently
triggered by increased sympathetic activity associated with ion channel genes have been identified, and currently molecular
acute emotional or physical distress. genetic testing is available for the KCNQ1, KCNH2, SCN5A,
KCNE1, and KCNE2 genes.62,63 LQTS has a prevalence of 1:1100
QT interval prolongation and TdP are more common in
women, possibly due to gender differences in ion channels.59 to 3000.65 Long QT syndrome is categorized as inherited (Jervell,
The baseline QT interval is longer in women than in men. Lange-Nielsen syndrome, Romano-Ward syndrome) or acquired.



44
Chapter 2




Figure 2.3 EKG of patient with long QT interval.


The ˜˜acquired™™ group are now considered to be silent mutation ventricular dysrhythmias are most easily triggered. The QT inter-
carriers in whom a specific trigger unmasks the condition.65 val normally shortens with increasing HR and shows circadian
The diagnosis of LQTS is based on clinical history, family his- periodicity with a nadir during sleep and a peak shortly after
tory, and EKG. Long QT Syndrome is symptomatic in approxi- awakening, corresponding to the hours when the risk of sudden
cardiac death is highest.67
mately 60% of patients. Clinical symptoms include syncope
(26“30%), seizure (10%), and cardiac arrest (9%), usually second-
ary to adrenergic arousal. In the 40% who are asymptomatic,
Torsade de Pointes
diagnosis is based on a family history or EKG and/or gene
testing.63 A positive family history includes a history of sudden A small minority of patients with QT prolongation from any cause
cardiac death in an immediate family member before age 30, or a are at risk for developing TdP. Torsade de Pointes is characterized
family member with a confirmed diagnosis of LQTS. Women with by phasic changes in amplitude and polarity of the QRS com-
a history of unexplained syncope, documented polymorphic VT, plexes so that the peaks appear to be twisting around an imagin-
or a family history of sudden cardiac death, should be carefully ary isoelectric baseline (twisting of the points).
screened for this disorder. At a minimum, this screening would
entail obtaining an EKG and a more detailed family history.59
Jervell, Lange-Nielsen syndrome (JLNS)
This syndrome, first described in 1957,68 is characterized by long
QT interval
QTc, (usually >500 ms), bilateral sensorineural deafness, and an
Prolongation of the QT interval is defined as a QT interval corr- autosomal recessive pattern of inheritance involving the KCNQ1
and KCNE1 genes.62 A deaf child experiencing syncope during
ected for HR (QTc) > 440 ms for males, and >460 ms for post-
pubertal females (see Figure 2.3). Optimal measurement of the physical exertion, fright, or stress is the typical presentation of
QT interval, which varies with HR and autonomic tone, is this syndrome. The syncopal episodes and occasionally sudden
obtained during a resting state with simultaneous recording of death, result because of triggered ventricular tachydysrhythmias
several limb leads, and measurement of the QT interval in lead II (VT, VT“TdP, VF) occurring in association with the prolonged QT
interval.69
(if T wave amplitude is reasonable). Using Bazett™s formula, the
QTc is obtained by dividing the measured QT interval by the
square root of the preceding R“R interval in seconds. The mea-
Romano“Ward syndrome
sured QT interval may also be compared against Simonson™s age-
and-rate adjusted normal range of values of the QT interval.66 This syndrome, described in 1963 by Romano and in 1964 by
A prolonged QT interval is generally taken to represent abnor- Ward, refers to individuals with normal hearing who have the
mal repolarization of cardiac muscle, and it is during the vulner- same prolonged QT interval, T wave abnormalities, propensity to
able relative refractory period of ventricular repolarization that develop syncope associated with ventricular tachydysrhythmias



45
1 Cardiovascular and respiratory disorders


(VT“TdP, VT, VF), as seen in JLNS. The pattern of inheritance is psychotropic drug therapy. Although hypocalcemia may prolong
autosomal dominant with varying expression.63 Cardiac events, the QT interval, it is seldom associated with the development of
more common from the preteen years through the 20s, may TdP. Torsade de Pointes is a rare complication of liquid-protein
occur at any age, from infancy onward.63 The fetus, due to modified-fast dieting in individuals who have had significant rapid
genetic dominance, has a 50% probability of inheriting the weight loss over a short period of time and exhibit QT prolongation
disorder.63 on EKG. Bradydysrhythmias can also cause TdP. Ventricular dys-
Management of these two syndromes is directed toward pre- rhythmias (some TdP in morphology) are implicated as a cause of
venting syncope, cardiac arrest, and sudden death. Current recom- syncope in 10% to 60% of patients with high-grade AV block and
mendations include avoidance of activities known to precipitate syncope, and in 4% to 7% with sick sinus syndrome and syncope.
syncope and avoidance of drugs known to prolong the QT interval. Some patients with MVP, who also have QTc prolongation, have a
Current therapies include beta-blocker therapy, insertion of car- higher prevalence of ventricular dysrhythmias.
diac pacemakers and implantable cardiac defibrillators.

Treatment
Acquired LQTS Treatment options include beta-blockers, pacemaker, auto-
mated internal cardioverter-defibrillator (AICD), and/or left cer-
Triggers for QT prolongation and TdP
vicothoracic sympathectomy. Untreated symptomatic LQTS is
Prolonged QT can be precipitated by drugs, electrolyte disturb- estimated to have >20% mortality rate in the first year of diag-
ances, hypothermia, and any cause of sympathetic stimulation nosis. Schwartz reported a decrease in mortality from 71% in
(Table 2.11).65 untreated patients to 6% in patients treated with beta-blockers.70
Increased caution is recommended when treating women However, beta-blocker therapy was ineffective in approximately
25% of cases.70
(pregnant and nonpregnant) with antidysrhythmic drugs. Class
Ia drugs (quinidine, procainamide, disopyramide) cause TdP with The goal of treatment is to prevent and treat any dysrhythmia
equal frequency.66 Class Ic drugs (flecainide, encainide, indecai- that can result from prolonged QT interval. Immediate therapy
nide, lidocaine), Class III drugs (amiodarone, sotalol), and preny- should include withdrawal of the offending agent(s) and correc-
lamine (coronary vasodilator) produce TdP less commonly.66 tion of any underlying electrolyte abnormality, hypothermia, and
Torsade de Pointes has not been reported with Class Ib drugs, cause of sympathetic stimulation. Failure to diagnose LQTS may
which shorten the QT interval, or with beta-adrenergic blockers or lead to continued use of the offending agent as well as adminis-
calcium antagonists. In about half of the patients, drug-induced tration of antidysrhythmic drugs capable of further prolonging
TdP occurs within the first three to four days of initiation of the QT interval, thus increasing the risk of developing a fatal
therapy, but late onset occurrence (months to years later), usually dysrhythmia.
in association with a change in drug dose, electrolyte imbalance, Beta-blockers are the first line of treatment. Beta-blocker ther-
or a bradydysrhythmia, is also seen.67 Warning signs of an apy plays a significant role in effectively suppressing ventricular
impending drug-induced TdP may be the new appearance of a dysrhythmias, which are often precipitated by sympathetic activ-
peculiar ventricular bigeminy with late cycle PVD and bizarre ity. In someone with LQTS, suppression of PVD may be beneficial
postpause T wave changes in association with a moderate QT as PVD may be a precursor of TdP or VT. In full doses, beta-
prolongation.66 Phenothiazines and tricyclic antidepressant adrenergic antagonists completely suppress or significantly
drugs, similar to quinidine electrophysiologically, increase the reduce the frequency of symptoms, although the QT interval
duration of the QRS complex, prolong the QT interval, and cause remains unaffected. A ˜˜full™™ (maximum) dose of propranolol is
T wave flattening with U wave prominence. These EKG changes that which is tolerated, or produces symptomatic bradycardia.
occur in about 50% of patients treated with phenothiazines Atenolol is a longer-acting cardioselective beta-blocker with
(thioridazine > chlorpromazine or trifluoperazine) and about fewer side effects than propranolol.
20% of patients treated with tricyclic antidepressants. Increased A permanent pacemaker, programmed to prevent bradycardia
ventricular irritability is a potential complication with therapeu- and pauses (anti-bradycardia pacing), which have the potential to
tic as well as toxic doses of these psychotropic drugs. Although the trigger a dysrhythmia, can be helpful when used in conjunction
with beta-blocker therapy.71 Temporary overdrive pacing is a
risk of TdP is relatively low, it has been documented to occur with
the majority of psychotropic drugs, thioridazine being implicated form of emergent therapy in the presence of a life-threatening
most often. Episodes of TdP are often preceded by abrupt sympa- dysrhythmia.
thetic activation, such as might occur with anger, fright, or sud- An AICD is indicated when symptoms (e.g. syncope) persist,
den awakening. and dysrhythmia is documented despite beta-blocker therapy,
or when the initial presentation is cardiac arrest.72 An AICD
Long QT syndrome is sometimes associated with central ner-
vous system diseases such as intracranial aneurysms, sub- reduces the incidence of sudden death when the episode of
arachnoid hemorrhage, acute cerebral thrombosis, and brain TdP is prolonged or proceeds to VF. Continuation of beta-
metastases. Torsade de Pointes can also be precipitated by severe blocker therapy is recommended when an AICD has been
implanted.72,73 In parturients with a pacemaker or an AICD,
hypokalemia and severe hypomagnesemia alone or in combina-
tion, and hypokalemia in combination with antidysrhythmic or the usual precautions should be taken to obtain a full history



46
Chapter 2



Table 2.12 LQTS: treatment in pregnancy

Clinical state Treatment Goal of treatment

Congenital LQTS
Benign LQTS “ Asymptomatic (no syncope history) þ no 1. # excess sympathetic activity
No prophylactic treatment
family history of sudden death or complex ventricular 2. Prevent and suppress
dysrhythmias ventricular tachydysrhythmia
3. Maintain uteroplacental
perfusion
a
Asymptomatic with family history of premature sudden Full dose beta-blocker
death or complex ventricular dysrhythmias
Symptomatic LQTS a. Full dose beta-blocker
a. !1 episode of syncope without prior treatment b. Consider pacemaker
b. Recurrent syncope despite beta-blocker Æ left c. Temporary overdrive pacing
cervicothoracic ganglionectomy
c. Sustained life-threatening
dysrhythmia (acute situation)
Drug-refractory LQTS syncope despite intensive drug Left cervicothoracic sympathetic
therapy or disabling drug side effects ganglionectomy
Chronic overdrive cardiac pacing
Recurrent cardiac arrest AICD
Acquired LQTS
Induced change in ECG pattern: prolonged QTc interval Discontinue causative drug Early recognition
(! 440 ms), " PVD Æ bigeminy, VT, Torsade de Pointes Correct underlying electrolyte & Treat cause
metabolic abnormalities Avoid drugs & conditions which cause
QT prolongation þ/or potentiate
(hypokalemia, hypomagnesemia,
hypocalcemia) ventricular dysrhythmias
Sustained Torsade de Pointes Electrical defibrillation
Prevention of recurrent malignant ventricular dysrhythmias Isoproterenol infusion
Cardiac pacing

a
Full dose: beta-blockers should be administered to the maximum tolerated dose/symptomatic bradycardia
LQTS ¼ Long QT syndrome; AICD ¼ automatic implantable cardioverter defibrillator; ECG ¼ electrocardiogram;
PVD ¼ premature ventricular depolarization; VT ¼ ventricular tachycardia




about the device and consult with the manufacturer or cardiol- Interpretation of fetal cardiotocographic monitoring during
ogist about management of the device throughout pregnancy, possible fetal distress may be difficult when full doses of beta-
especially peripartum. adrengergic blocking drugs are administered to the mother, or
Left cervicothoracic sympathectomy is reserved for patients when there is a possibility that the fetus may have inherited the
who are refractory to other types of treatment.65 Genotype- cardiac conduction defect. Monitoring for fetal acidosis with

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