Episode 3: The Tachycardia Thats Too Slow

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Here I am, back with my third blog post. I must mention it was heartening (pun intended) to receive a plethora of feedback on my last post. The post was about heart monitoring devices and explored the role of implantable loop recorders (ILRs) and ECG machines in arrhythmia diagnosis. Feedback means people are listening, watching and reading. That’s a good feeling.  Speaking of feedback, my post today dwells on remote home monitoring devices and if their feedback capabilities can and are being optimally utilized in the world of EP.

Over the years, the capabilities of implanted heart devices have grown exponentially, both in their therapeutic and diagnostic functions. However, this has translated into an increased burden on device clinics, as there is a large quantity of data being captured, which needs to be analyzed. This means specialists need to allocate more time to clinic patients. The increased longevity of patients, while a desired outcome, also means, that the device clinic must allocate more resources per patient over the years.

Thankfully, with the advent of remote monitoring for implanted devices, the workload of routine analysis at physical clinics has begun to plateau. Such devices provide periodic telemetric transmission of patient’s heart readings via the internet to a secure cloud server. These readings can then be assessed by medical teams located at ‘virtual clinics’. They allow for early diagnosis of conditions and scheduling of physical visits, only when necessary. Over a period, this helps dodge acute complications in several cases. However, I think, the medical community is not completely prepared for a totally remote management of cases via such devices. To support my thought, I will present the case of a very close patient of mine.

Case Study:

A 72-year-old male with ischemic cardiomyopathy and severely reduced global systolic function, the ejection fraction or the capability of the heart, to pump out blood to the rest of the body, was reduced to 19%. To reduce the load on his heart and to synchronize the pumping of blood through his system, the patient was fitted with a CRT-D, a resynchronization therapy where the device functions as a cardiac pacemaker and doubles up as a defibrillator. In this case. His CRT-D also includes home monitoring; the overlying topic for this blog post. Additionally, the patient is on a daily dose of amiodarone (brand name: Procar), which helps lower heart rate & the number of ‘tachycardic’ events. Do note, the patient is 100% dependent on the pacemaker in order to have an underlying rhythm and pump blood.

The patient presented on our “virtual clinic” with three days of reduced CRT pacing, manifesting physically as weak and unable to carry out tasks previously capable of, like walking up the stairs. On the analysis of the home monitoring data, we noted, only a reduced CRT pacing, which didn’t give away much. Here’s a look at the graph extracted from the Biotronik home monitoring system.

Biotronik Graph Analysis

The two-axis represents the percentage of pacing and the time (in days). Grey circles denote atrial pacing; blue is for right ventricle pacing and the fuschia triangles denote left ventricle pacing. The reduced CRT pacing appears to be a dangerous situation because this means the patient isn’t being paced 100% of the time, especially as he is a patient who is known to be pacing dependant. However, I cross-checked with his arrhythmic events diary to find a probable cause but there wasn’t any occurrence during these pacing drops. To investigate further, we called him in to for a device analysis and ECG.

before treatment VT egm.png

Biotronik EGM/ECG Analysis

As we read the ventricle marker channels, we noticed sense events in left, as well as right ventricle. In the third line, we saw a wide complex signal, not a standard normal signal. Now if you study the atrial signals below and compare it to ventricle signals, we know that there are more ventricle signals compared to the atrial signals. Getting to our basics, we know that when V is greater than A, it’s a ventricular tachycardia (VT).

Now the question came up, why didn’t his defibrillator pick up on this slow VT and treat it accordingly?

It could have been either of the two reasons:

1) the defibrillator was not reading the signal

2) it could not diagnose it.

However, we saw that there were signal readings on the marker channels which implies that the lack of diagnoses was the issue. Just looking squarely at the VT reading, it is about 90 beats per minute. That VT is under the VT cut-off, and not just Biotroniks cut-off, but no other implanted defibrillator device can diagnose such a reading. While 90 beats per minute is not as dangerous as say 180 beats per minute, it is terrifying for a patient with just 19% pumping capacity. A minor activity such as a flight up the stairs, during such an episode, can lead to worsening of the situation.


The patient was called into the clinic and treated with aggressive Anti-Tachycardia Pacing (ATP). To explain simply, an ATP is a form of localized stimulated pacing used to treat tachyarrhythmia, by pacing faster than the arrhythmia. It can be executed using an implanted device.

How does it work?

Well, if the VT is at 120 beats per minute, we pace the ventricles at 140 beats per minute, aiming to break the re-entry cycle. In the case of this patient, we manually paced him at 110 beats per minute and broke the cycle.

Post this event, and owing to repeated events that were reported, we admitted him and gave him a VT ablation using 3D mapping.

It has now been three years and the patient has been free of any episodes. 


Food for Thought

As we come to the end of this post, I would like to leave you with food for thought. We spoke about “virtual clinics”. But who exactly is monitoring the remote readings at such clinics? The case discussed above was a yellow alert event for the device, despite it being of an urgent nature. Typically, these messages would arrive at the “virtual clinics” only the next day. We were successful in this case because we could manually diagnose this, in a timely manner by knowing our patient and carefully analyzing two different reports and making the connection. Now imagine, usually, there are very well educated nurses manning these “virtual clinics”.

However, are they equipped enough to make advanced diagnoses like we just did?

That is something, we need to think about.

 Here at EPme.me we love feedback; our aim is to help you learn so please do get in touch with ideas for sessions you’d like to see. Whether you work in electrophysiology, devices, both or neither, we want to hear from you. Follow our YouTube channel to keep up to date with leading cardiac electrophysiology from around the world. Sign up for our newsletter to receive our free ECG cheatsheet  – you’ll wonder how you did without it.

COMING UP: Next few weeks, we're gonna be talking about using devices in arrhythmia diagnosis. Some really interesting case studies from devices, to explore further the effects and use of devices in EP.

Thank you so much!