Chapter 17 Ventricular Arrhythmias and Sudden Cardiac Deathdrugs and present with few episodes of torsades de
pointes in whom the QT remains long. (Level of
Evidence: C)
Sodium channel blocker-related toxicity
Recommendations
Class I
In patients with sodium channel blocker-related
toxicity, removal of the offending agent is indicated.
(Level of Evidence: A)
Class IIa
1 Stopping the drug, reprogramming the pace-
maker or repositioning leads can be useful in patients
taking sodium channel blockers who present with
elevated defi brillation thresholds or pacing require-
ment. (Level of Evidence: C)
2 In patients taking sodium channel blockers who
present with atrial fl utter with 1:1 AV conduction,
withdrawal of the offending agent is reasonable. If
the drug needs to be continued, additional A-V
nodal blockade with diltiazem, verapamil, or beta-
blocker or atrial fl utter ablation can be effective.
(Level of Evidence: C)
Class IIb
Administration of a beta-blocker and a sodium
bolus may be considered for patients taking sodium
channel blockers if the tachycardia becomes more
frequent or more diffi cult to cardiovert. (Level of
Evidence: C)
Other drug-induced toxicity
Recommendations
Class I
1 High intermittent doses and cumulative doses
exceeding the recommended levels should be
avoided in patients receiving anthracyclines such as
doxorubicin. (Level of Evidence: B)
2 All patients receiving 5-fl uorouracil therapy
should receive close supervision and immediate dis-
continuation of the infusion if symptoms or signs of
myocardial ischemia occur. Further treatment with
5-fl uorouracil must be avoided in these individuals.
(Level of Evidence: C)
3 Patients with known cardiac disease should have
a full cardiac assessment including echocardiogra-
phy, which should be undertaken prior to use of
anthracyclines such as doxorubicin, and regular
long-term follow-up should be considered. (Level of
Evidence: C)Ongoing trials and future directions
There remain a signifi cant number of unexplained
sudden cardiac deaths. Registries continue to collect
information and tissue samples relating to these
deaths, hoping to identify biomarkers or genetic
clues. There are several ongoing trials exploring the
value of new and simpler techniques of resuscita-
tion. The value of automatic external defi brillators
is being actively assessed in a variety of community
settings.
Sudden cardiac death continues to occur in
patients without previous cardiac disease. Risk
factors for the prediction of sudden cardiac death
and for ICD indication are imperfect, relying for the
most part on estimates of left ventricular function.
A number of large scale trials and many small studies
search for better risk factors in a wide variety of
disease states, for example post MI, dilated cardio-
myopathy, hypertrophic cardiomyopathy, Brugada
syndrome, end-stage renal disease, diabetes, ath-
letes, muscular dystrophy, etc.
The risk predictors of T wave alternans, heart rate
variability such as heart rate deceleration capacity
and turbulence are being intensively investigated.
Recently, the results with microvolt T wave alter-
nans have been disappointing. The ABCD clinical
study, which was designed to determine if a T-Wave
Alternans (TWA) test is equivalent to an Electro-
physiology Study (EPS), reported that both tests
were only modestly valuable but the combination
was superior. The MASTER II (Microvolt T Wave
Alternans Testing for Risk Stratifi cation of Post MI
Patients) failed to identify post-MI patients at higher
risk of sudden cardiac death.
There are several ongoing studies of novel antiar-
rhythmic and other therapies (for example hormone
replacement, omega 3 fatty acids, statins, angioten-
sin receptor blocking agents) for the reduction of
sudden death and ventricular arrhythmias in large
post MI or heart failure populations and in specifi c
situations such as the long QT syndrome.
There is a surprising number of small trials of
ICD therapy for primary prevention of sudden
cardiac death in miscellaneous populations. One
large ongoing study is the MADIT-CRT trial which