subcutaneous icd may be proposed to patients with channelopathies presenting with significant risk for sudden cardiac death .
short qt syndrome is a rare channelopathy carrying the risk for inappropriate therapies with current transvenous icd because of overdetection of the ample t wave .
we report on the uneventful followup after implantation of a subcutaneous icd in a patient with a short qt syndrome .
because patients with short qt syndrome ( sqt ) may have tall peak t waves with short qrst intervals , inappropriate icd therapies may occur due to the possibility of double counting of both the qrs and the t wave 1 , leading to a succession of short cycle lengths , as realized for example during exertion .
inappropriate icd therapies have been described earlier in sqt patients with transvenous icd , which should be prevented by tailoring the detection window characteristics 2 .
if such an hazard may happen with subcutaneous icd  whose ability in avoiding t wave detection is crucial  is unknown , since no sqt case seems to have been reported with such a device as yet . a 30 yearold man with sqt syndrome implanted for 9 years with a transvenous icd for primary prevention ( familial sudden death due to sqt and induction of ventricular fibrillation )
his ecg showed ample t waves with 280 ms qt interval ( corrected qt 330 ms ) .
we decided to reimplant the icd , using a subcutaneous icd ( sicdtm system , boston scientific , st .
paul , mn , usa ) . after assuring an acceptable r / t ratio using the screening ruler ( fig .
1 ) , the pulse generator was placed subcutaneously in the anterior axillary line with the electrode inserted subcutaneously parallel to the sternal midline .
ventricular fibrillation was induced and terminated by a 65 j shock ( 15 j safety margin ) .
below are shown the acceptable r / t ratio using the screening ruler both at implant ( left ) and at 1 year ( right ) .
testing of the device at baseline , during treadmill or during the followup never displayed t wave over sensing in any detection configuration (  primary  between the pulse generator and the proximal electrode ,  secondary  between the generator and distal electrode , or  alternate  between both electrodes ) .
2 ) even if there are a few missed r waves at exertion in some configuration ( arrows ) , especially when the r wave amplitude slightly decreases ( the subcutaneous icd uses a two peak average to adjust the detection profile dynamically , but in the presence of varying amplitudes such as during exertion , a few beats may be missed while adjusting to the underlying amplitudes ) .
the latency sometimes observed after the r wave on markers ( red circle ) in the alternate configuration is an artifact of programmer telemetry 's ability to process increased marker activity , for example , exertion scenario at followup ( such a behavior is not observed in the ambulatory setting ) .
programmer telemetry recordings in the primary ( a ) , secondary ( b ) and alternate ( c ) detection configurations at implant , during exertion and at rest at 1 year followup .
s are the markers of the qrs complexes as sensed by the device ( see text for detailed explanation ) . at 1 year
followup , the r wave was 1.1 mv while t wave was 0.2 mv on ecg ( r / t ratio = 5.5 ) ( fig ) .
the r / t ratio was higher at implant during treadmill and during the followup in the primary configuration ( table 1 ) .
amplitude and qrs : twave ratio measurements from three time points : implant , exertion and followup the patient was discharged in the primary configuration and no appropriate or inappropriate detection ( fig .
short qt syndrome is a very exceptional channelopathy carrying a significant risk of sudden cardiac death due to malignant ventricular arrhythmias 3 .
sqt is caused by an excessive abbreviation of repolarization duration , mainly due to some inherited gain of function in potassium channels 3 .
sqt is diagnosed if corrected qt is 330 ms or 360 ms together with clinical events 4 .
risk stratification to date only refers to spontaneous clinical events such as unexplained syncope or a previous cardiac arrest 4 .
icd is the only recommended therapy , although medical treatment with quinidine may be used in selected cases 4 .
patients with sqt syndrome often present with tall peak t waves together with the short qt interval 1 .
thus , inappropriate icd therapies have been described , using transvenous icd because of double counting of both the qrs and the t wave 1 , especially during exertion . of note , this may be prevented by tailoring the detection window characteristics 2 .
if such hazard may happen with subcutaneous icd  whose ability in avoiding t wave detection is crucial  is unknown , since no sqt implanted with subcutaneous icd seems to have been reported as yet .
this case highlights the fact that patients with sqt syndrome may also benefit from subcutaneous icd .
due to morbidity and complications inherent to transvenous icds , sqt syndrome may also benefit from subcutaneous icd
. however , additional cases are needed to affirm the safety of such device in this setting , especially in patients with ampler t waves .
 key clinical messageshort qt syndrome carries the risk for inappropriate therapies using transvenous icd because of overdetection of the ample t wave . 
 sqt syndrome may also benefit from subcutaneous icd , although additional cases are needed to affirm the safety of such device in this setting . 
Introduction
Case presentation
Discussion
Conclusion
Conflict of Interest