Vol. 2 ECG and QTc ramblings
How comfortable are you with increasing methadone doses over 100mg?
The newsletter has a more clinical flavour this week. This wasn’t the topic I was planning to write about but then, once I got started, I realised it opens up a lot of cans. Some of them with worms.
In 1997, I was a junior house officer in Raigmore Hospital, Inverness, and there were no health care assistants or nurses trained to do ECGs.I spent a lot of time pushing around the ECG machine trolley. As well as the beige VCR-like block of the machine itself the trolley carried all the accessories: the leads, the sticky pads, the weird NHS plastic razors to cope with the more hirsute individuals. Every single person who was admitted needed a ECG and most needed several. I soon got slick and prided myself at my ECG skills but it was time-consuming. I counted myself lucky as my mate working down the road in Aberdeen had an older system which involved using blobs of gel and little vacuum suckers to fix the electrodes to the chest. One of those little suckers pinging off as you were getting a 12-lead trace meant you were back to square one. Those machines could, and often did, reduce fatigue-addled junior doctors to tears.
The point is that while full 12-lead ECGs are a little more portable these days they are fundamentally still a bit of a pain in the arse. The patient has to be undressed, sticky-wired up, and the ECG can be collected. If they are trembly or a bit fidgety it’s harder. And, that isn’t uncommon if you are rattling or have recently necked some amphetamines… Getting ECGs from a load of patients lined up in a Nightingale ward was tedious but didn’t present any major challenges. No one was missing for a start. Add in a patient population who are prone to missing appointments, are intrinsically suspicious of medical services (often for very good reason), or who might be getting seen in a non-clinical environment, and it can start to get more tricky.
Tricky is the last thing we need when it impacts on someone’s methadone dose.
One of the papers I covered in the last Addiction Professionals’ Clinical Update was this one about using a smartphone iECG device to measure QTc intervals. I am still driven a little demented by the clinical concerns around the QTc interval. The lack of hard evidence sets my teeth on edge as it has felt, for a long time, that clinical practice has been determined with roughly the same level of accuracy as a weatherman who licks his finger and sticks in the air.
There is too much we don’t know. Simply understanding the absolute risk of a raised QTc in our group of patients is where we need to start. And, what is the incremental differences in treating someone with 80mg, 100mg, or 120mg of methadone? It is only by comparing these absolute risks can we determine the best course of action. Naturally, when the QTc comes into play then flipping to buprenorphine preparations are a good option. Yet, despite the dearest wishes of the pharmaceutical industry who keep churning out novel buprenorphine preparations, it is just not for everyone.
If we can properly weigh up the risks versus benefits then we can have grown up conversations and people can decide for themselves. At present, we don’t have that information so we end up falling back on a position where the prescriber feels they carry the responsibility - and when the risk is unquantifiable the response is usually to simply withhold increased doses, no matter the harm of sub-optimally treated opiate dependence.
And, here’s something that may smart a little: I suspect some clinicians are very happy to hold down the dose of methadone. There might be a touch of the anti-methadone ideology lingering or just a simple discomfort with prescribing higher doses. I have even wondered, on occasions, whether there is just a sense that the person has enough methadone and now it is down to them. Sometimes the “we can’t consider more methadone until we have an ECG” gambit is aligned with some deep seated, largely sub-conscious, beliefs. Yet, we know that the metabolism of methadone is highly variable and the dose that holds someone is not easy to predict.
My experience is that there is an unease with people being on doses over 100mg and we know that many people are chronically under-dosed, barely hitting a therapeutic 60mg. The QTc interval has legitimised those concerns and I am not convinced that the evidence exists to allow us to make those judgements. This could be where the precautionary principle kicks in and that is a fair argument. I’m just wary about that position when it means we prescribe less of a medication that has been as stigmatised as any in history.
The smartphone iECG paper - an addendum
This week I realised I hadn’t quite picked up on the full picture on this paper when I wrote about it for the Update. I had been browsing Kardiocor devices and had a sudden thought. In my little brain I had assumed that the iECG smartphone device was spitting out the QTc interval automatically.
I went back and checked. The paper mentions digital calipers and manual calculation. Hmm, I thought. I emailed the corresponding author to check and he responded very promptly and very courteously telling me that, yes, unfortunately, the devices don’t calculate it themselves. It was worked out manually for the study. That is a bit of a blow.
It is worth dwelling on how very different this iECG device is from the current process for 12-lead ECGs. Naturally, we still need 12-leads but it offers the promise of sunlit uplands for people sick of stick labels and tangled leads. All the patient has to do is push their fingers down on the two little sensor pads. Very cool. They are also ridiculously affordable at $89. Unfortunately, for the moment, you will need to some calipers and someone who knows how to calculate a QTc manually to make this work in practice. We live in hope though.
Reducing the barriers
I have gone on about ECGs and the QTc at length but it feeds directly into one of my major bugbears about services. Barriers. They creep up all the time and we need to be constantly vigilant. I’m prepared to accept that the raised awareness of QTc and methadone concerns may be doing a tremendous amount of good to reduce medication-related harms. However, that needs to be weighed against the other harms. And, holding methadone doses down is one of them.
It doesn’t look like the little smartphone iECGs are quite ready to help break down this barrier.
Forthcoming webinar | 21 September 2021
I am going to be doing a webinar for Addiction Professionals next month. More details:
More to come…
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Other than in the Coronary Care Unit where the nurses, oh the joy, could do them. I rarely went there though and left it, as much as possible, to the SHOs and Registrars, as it was just a bit too scary.
As an aside, have there been any other others? Thalidomide? After that, I have nothing.