A failed conversion test consists of 2 consecutive induced arrhythmia episodes that failed to convert at 65 J.
Factors that increase defibrillator threshold:
(1) adipose tissue between coil and sternum
(2) generator malposition along anteroposterior axis
(3) fat between the generator and the rib cage of the thorax
Parameters:
(1) number of coil widths of fat tissue between the coil and the sternum or ribs (as seen on lateral chest X-ray)
(2) position of the device relative to the lateral midline (near the anterior axillary line, as seen on the lateral chest X-ray)
(3) amount of fat tissue between the most medial point of the device and the lateral aspect of the rib cage (as seen on an AP chest X-ray)
(4) body mass index
|
Parameter
|
Finding
|
Points
|
|
number of coil widths
|
<= 1 coil width
|
30
|
|
|
1.01 to 2 coil widths
|
60
|
|
|
2.01 to 3 coil widths
|
90
|
|
|
> 3 coil widths
|
150
|
|
position relative to lateral midline
|
on or posterior to midline
|
x1
|
|
|
anterior to midline
|
x2
|
|
|
entire generator is anterior by > 1/2 width
|
x4
|
|
amount of fat tissue
|
< 1 generator width
|
x1
|
|
|
>= 1 generator width
|
x1.5
|
|
BMI
|
<= 25 kg per square m
|
40
|
|
|
> 25 kg per square m
|
0
|
where:
• The broad width of the device is seen in the lateral X-ray.
• The narrow width of the device is seen in AP views.
subscore =
= (points for coil widths) * (factor for lateral position) * (factor for fat tissue)
total score =
= subscore - (BMI factor if subscore >= 90 else 0)
Interpretation:
• minimum score: 30
• maximum score: 900
|
Total Score
|
Risk Group for Cardioversion Failure
|
|
< 90
|
low risk
|
|
90 to 149
|
intermediate risk
|
|
>= 150
|
high risk
|
