1/ *Can we see Torsades coming?*
A few months ago, I had the chance to study the rhythm changes leading up to an episode of Torsades. Discussed here -
This helped me pick up some "warning signs" that may help facilitate early recognition.
#tweetorial
A few months ago, I had the chance to study the rhythm changes leading up to an episode of Torsades. Discussed here -
This helped me pick up some "warning signs" that may help facilitate early recognition.
#tweetorial
2/There are 3 critical substrates for Torsades:
(i) Prolonged action potential (long QT)
(ii) Early afterdepolarizations (EAD)
(iii) Dispersion of repolarization (DR)
(i)A long QT is essential but not sufficient. E.g. Amiodarone prolongs QT but reduces DR - low risk of Torsades.
(i) Prolonged action potential (long QT)
(ii) Early afterdepolarizations (EAD)
(iii) Dispersion of repolarization (DR)
(i)A long QT is essential but not sufficient. E.g. Amiodarone prolongs QT but reduces DR - low risk of Torsades.
3/ (ii) EAD = depolorization during phase 2/3. In long QT, a longer phase 2 period increases the chances of EADs. However, not every long QT develops EAD so other mechanisms may be involved.
(iii) DR = heterogenous repolarization properties within the myocardium: PMID: 16253930.
(iii) DR = heterogenous repolarization properties within the myocardium: PMID: 16253930.
4/ Although torsades is "initiated" by EADs, it is likely "maintained" by reentry mechanisms facilitated by DR.
Now let's focus on EADs. They are responsible for the "R" in the "R-on-T". They are also likely responsible for some of the EKG changes leading up to Torsades.
Now let's focus on EADs. They are responsible for the "R" in the "R-on-T". They are also likely responsible for some of the EKG changes leading up to Torsades.
5/ Again, EADs don't always result in Torsades (if not followed by reentry). Importantly, their electrical effects can be picked up on a surface EKG. The pattern of EKG findings depend on whether the EAD was propagated (technical term = triggered activity) or not.
6/ (i) EAD not propagated - this would result in repolarization abnormalities - the giant T-U wave (T and U waves are often fused and difficult to distinguish).
This has been systematically studied: PMID: 19573731. Abnormal T-U waves directly preceded Torsades in 34/35 patients!
This has been systematically studied: PMID: 19573731. Abnormal T-U waves directly preceded Torsades in 34/35 patients!
7/(ii) If the EAD is propagated -this would result in a PVC right after the giant T-U wave
PVCs are usually accompanied by ST-T aberrancies (just like bundle branch blocks). However, you combine this with EADs and it results in "bizarre" ST-T changes.
Example from that article
PVCs are usually accompanied by ST-T aberrancies (just like bundle branch blocks). However, you combine this with EADs and it results in "bizarre" ST-T changes.
Example from that article
8/ Importantly, since EAD is facilitated by longer action potential duration (APD), the amplitude of the 'post-pause' EADs would be higher.
This can happen when a PAC/PVC resets the sinus node and the next sinus beat is delayed. This delayed beat will have a longer APD.
This can happen when a PAC/PVC resets the sinus node and the next sinus beat is delayed. This delayed beat will have a longer APD.
9/ If the amplitude of the post-pause EAD is high enough, it may propagate and cause a PVC. This PVC will reset the sinus node and cause another pause and so on.
This produces a bigeminal pattern called "short-long sequence", the initiation of which was demonstrated in our case.
This produces a bigeminal pattern called "short-long sequence", the initiation of which was demonstrated in our case.
10/ When you see this pattern, Torsades is absolutely imminent.
Found a similar example on LITFL - litfl.com/cardiac-megaco…
A few weeks later I had saw this pattern again in a patient who was started on scheduled Reglan. 2 g Mag over 10 minutes resulted in obvious improvement.
Found a similar example on LITFL - litfl.com/cardiac-megaco…
A few weeks later I had saw this pattern again in a patient who was started on scheduled Reglan. 2 g Mag over 10 minutes resulted in obvious improvement.
11/ I have no doubt in my mind that patient would have had Torsades had I not administered the Mag.
Side-note -
It's also important to not confuse this pattern with ischemia. Although the PVCs may have discordant ST changes, careful assessment of the sinus beats will be helpful.
Side-note -
It's also important to not confuse this pattern with ischemia. Although the PVCs may have discordant ST changes, careful assessment of the sinus beats will be helpful.
12/ Summary:
(i) As telemetry is ubiquitous in the ICU, an astute pair of eyes may be able to 'see Torsades coming'
(ii) Pattern-recognition: Giant T-U waves (especially post-pause) +/- "bizarre" bigeminy
(iii) Once you see this, determine the QT/U. If prolonged start treatment!
(i) As telemetry is ubiquitous in the ICU, an astute pair of eyes may be able to 'see Torsades coming'
(ii) Pattern-recognition: Giant T-U waves (especially post-pause) +/- "bizarre" bigeminy
(iii) Once you see this, determine the QT/U. If prolonged start treatment!
13/ Treatment of Torsades deserves a separate discussion but some key points can be found here -
Feel free to spread the word!
Feel free to spread the word!
