The road to hell is paved with good intentions.
Not
OK
Not
OK
VF !
VF ?
Shock
OK
Not
OK
Reversed
polarity
Shock
OK
Not
OK
Combo
shock
Shock
OK
Shock
OK
Photo by Chris Rea
Sami Viskin
2010
The Top-10 Reasons to avoid DFT testing.
Reason # 1
The vast majority of patients with
implanted ICD will never have VF
Distribution of ICD-treated arrhythmias by heart rate and morphology.
223 patients
CAD + ICD
Number of events.
140
43% NSVT
43% SMVT
16% VF
VT = 57%
100
60
VF = 3%
20
270
230
200
170
140
VT rate (beats/min)
Wathen, Circulation 2001
The Top-10 Reasons to avoid DFT testing.
Induced VF = spontaneous VF.
Different
provocation.
Different
characteristics.
Electrically induced VF
vs. Ischemic VF
DFT in dogs.
External Biphasic shock
Defibrillation efficacy
using DFT x 1.5
60%
40%
300
20%
150
AC current Ischemia
Walcott, JACC 2002
Induced VF Spontaneous
during
VF during
ischemia
ischemia
Qin, Circulation 2002
Its all about probabilities.
Assume the system has 95%
defibrillation success.
5% of the shocks will fail.
Lessons from SCD-HeFT:
ICD testing: limited
to 2 VF inductions:
Data for 717 patients.
SCD-HeFT
Protocol
VF induction
98%
20 joules OK
20 joules not OK
VF induction
0 (zero)
10 joules OK
OK = Implant
30 joules not OK
Never mind = Implant
Survival
The Top-10 Reasons to avoid DFT testing.
DFT < 10 J
DFT > 10 J
The Top-10 Reasons to avoid DFT testing.
Defibrillation of:
Induced VF = Spontaneous VF.
Study
LESS
Implant criterion
DFT++ < 15 J
Programmed
shock
Shock failure
in real life VF
5 J > DFT++
11%
Max = 31 J
12%
PainFree
10 J safety
DFT + 10 J
13%
Sterns
10 J safety
Max = 30 J
17%
Swerdlow: The dilemma of DFT testing. PACE 2007
Impact of ischemia and reperfusion on defibrillation requirements
Defibrillation efficacy using shocks 1.5 times
the DFT for electrically induced VF
80 %
60 %
40 %
76%
40%
20 %
23%
0
Electrical VF
during ischemia
Spontaneous VF Spontaneous VF
during ischemia during reperfusion
Qin, Circulation 2002.
Bianchi, PACE 2009
291 patients
ICD implantation.
1.0
.98
.96
.94
.92
Sudden
Sudden death
death rate
rate
5
2 centers
10
15
20
3 centers
Total
Total Mortality
Mortality
DFT
always
DFT
never
1.00
No DFT
.95
.90
137
LVEF = 27+ 5%
154
26+4%
ß-Blocker = 57%
72%
Diuretics = 64%
87%
DFT
.85
.80
5
10
15
20
Follow-up (months).
291 patients
ICD implantation.
2 centers
3 centers
1.0
.98
.96
.94
.92
Sudden
Sudden death
death rate
rate
5
DFT
always
137
DFT
never
154
10
15
20
Total
Total Mortality
Mortality
1.00
No DFT
.95
.90
LVEF = 27+ 5%
26+4%
ß-Blocker = 57%
72%
Diuretics = 64%
87%
DFT
.85
.80
5
Bianchi, PACE 2009
10
15
20
Follow-up (months).
The Top-10 Reasons to avoid DFT testing.
Long-term survival may not necessarily
be affected by DFT testing.
Combined analysis of studies comparing mortality
in patients with and without DFT testing.
Odds ratio and 95% confidence limits
Russo. HeartRhythm 2005
Pires. JCE 2006
Bianchi, PACE 2009
0.5
1
2
Favors DFT testing Favors no DFT testing
Viskin, Heart Rhythm 2008
The Top-10 Reasons to avoid DFT testing.
DFT testing is not without risk.
Percentage of patients with cardiac
enzyme elevation during DFT testing.
40
49 patients
30
LVEF 34%
VF = 4.8+1.5
Shocks = 7+2
20
25%
37%
10
6%
0
CK
14%
CK-MB cTNT cTNI
The Top-10 Reasons to avoid DFT testing.
DFT testing is not without risk.
Canadian Registry: >19,000 ICD implantations.
• 80% underwent DFT testing.
35 (0.18%) had a lethal, potentially lethal
or disabling complication from DFT testing.
If you keep doing DFT testing sooner
or later you will have a patient with
lethal or disabling complication from
this œŧξώЂЉҖ test.
Prognostic Importance of Defibrillator
Shocks in Patients with Heart Failure
Hazard Ratio for Death (95% CI)
Hazard Ratio for Death (95% CI)
Appropriate shock
Inappropriate shock
5.68 (3.9 – 8.1)
1.98 (1.3 – 3.05) p=0.002
Any shock
0.5 1.0 2.0 4.0 8.0 16.0
A reasonable argument can be made that
defibrillation testing is unwarranted. The
risk and cost of defibrillation testing are
likely to outweigh the remote possibility
that a rare patient might benefit from it.
Gust Bardy, for the SCD-HeFT instigators.
N Engl J Med 2005.