An ICD (implanted cardioverter defibrillator) as imagined by AI – ChatGPT. In reality they are about 1 3/4inches across inside a smooth metal casing. In the event of a serious heart malfunction or if it stops beating the task of the ICD is to restart the heart with a normal rhythm and prevent sudden cardiac death.
Shock from pacemaker/defibrillator
23 November 2024
Irregular heart beats are common but mine is of a rarer kind which can lead to sudden cardiac death. Medical intervention has meant that I have continued to lead a normal healthy active life, until Friday 22nd November 2024.
I have had a very advanced pacemaker/defibrillator (an ICD) in my chest since 2019 – five and a bit years now. It has the power to deliver a severe electric shock (800 to a thousand volts for just a few milliseconds) to “re-set” or restart my heart if a problem develops. It has never self activated before. My assumption has been that the drug I am on, bisoprolol. and the pacemaker itself which prevents the heart rate from dropping below 50 beats per minute were enabling me to live a normal life as if I had no heart problem.
Only felt faint
But on Friday 22nd November, about 1pm, I was leaving the photographic portrait exhibition in The National Portrait Gallery and about to go down the stairs when I began to feel faint and feel that I might collapse at any moment. I held on to the rail at the top of the stairs and called down to Julie, my wife, who was several steps ahead of me. She was unaware that I had stopped following her.
She came up to me and I was still holding onto the rail and leaning against the wall. She said “Put your head down”. Good advice if you feel you are about to faint. I leant forward and then decided to sit down on the floor. I didn’t feel able to stand any longer. I was now conscious of the heavy thumping of my heart but after a short while, maybe about five seconds, it was beginning to feel more normal. I remembered my new watch which had a heart monitor on it. The thumping had died away. The reading was 70 and falling. I thought the reading was unlikely to be accurate.
A passer-by looked down at me sitting on the floor and offered help. I said I was OK thank you.
Apparent recovery – then the shock
After perhaps a couple of minutes I felt I was back to normal, stood up and started to go down stairs. Again Julie was a few steps ahead of me.
I descended the first short flight of steps and got half way down the next short flight when I half doubled up and let out a loud “Ooh!” as I felt a big punch to my chest, something which is often described as like being kicked in the chest by a horse. Not a bad description. I knew I had just experienced the defibrillator in action.
I carried on down the steps and entered a sort of lobby area where there happened to be a bench. I thought it might be a good idea to rest there for a few minutes to reassure myself I was OK to carry on my day and to adjust to the fact of what had just happened.
After that I went and collected my coat and bag from the cloakroom and we went and had a half of bitter and lunch in the upstairs comfortable and busy dining room in the nearby Chandos pub. The serving was slow but the food was quite good.
What had triggered this fainting and electric shock?
I can only speculate. Certainly it was not extreme exercise or heavy lifting. It was unusually cold, so what? When we got on the bus to come along Fleet Street I hadn’t quite got to my seat when the bus jolted violently forward almost throwing me to the ground, but I grabbed hold of something and saved myself from hitting the ground. I think I banged my chest against the hard edge of a seat or an upright pole. I’m not sure what. But I felt OK. Did this shock upset the ICD in some way? Or was the ventilation poor in the gallery and I was short of oxygen? Or were my blood sugars low as it was nearly lunch time? A mystery.
Should the ICD have given me the shock?
I had begun to feel normal and able to cary on my day and the shock was delivered, not when I began to feel faint, but ten or more seconds after I thought I had recovered. I’ll discuss this with the pacemaker team in Brighton when I see them next week.
Follow up
During Friday night the pacemaker monitor under my bed picked up the heart incident and using the mobile phone network automatically communicated with the pacemaker clinic in Brighton with all the data of the incident. This info would await the team when they arrived for work on Monday morning.
On the Saturday I phoned the pacemaker clinic in Brighton and left a message about what had happened.
The rest of our day
After lunch, at a quarter to three we left to go to the nearby National Gallery. We were surprised to see queues to get in. We had never seen anything like it here before. The queue was four or five deep and about fifty yards long. The weather was bitter cold so we decided queueing was not for us and returned to the National Portrait Gallery round the corner.
On the Saturday and since I have felt normal health-wise but concerned that seemingly nothing had triggered the defibrillator incident.
Consequences – Driving ban
I spoke with the pacemaker team in Brighton on the Monday morning. They had full details of what happened from their download of data and could see my evolving heart rate, second by second, for the five minutes that something was going wrong. Apparently the heart rate went up to 200 beats per minute.
They have been in touch with the consultant who is overseeing my case and he has requested some tweaking of the settings in the pacemaker. I have an appointment for Tuesday 3 December.
I now have to notify the motoring authorities (DVLA) about what happened and I will be banned from driving for a minimum of six months!
Thursday, six days after the event, I have resumed my morning jogging but I started with a much shorter run than usual.
DR 29 November 2024.
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From Chat GPT
Implantable cardioverter-defibrillator (ICD) – power of
An implantable cardioverter-defibrillator (ICD) delivers an electrical shock to correct life-threatening arrhythmias, such as ventricular fibrillation or ventricular tachycardia. The power and energy delivered during the shock depend on the ICD’s programming and the patient’s needs.
Energy Delivered: ICDs typically deliver shocks in the range of 20 to 40 joules. Some devices may go up to 50 joules, but this is less common.
Voltage: The voltage during a shock can be as high as 800 to 1000 volts, depending on the device and the impedance of the tissue.
Current: The peak current delivered can range from 30 to 40 amperes, again depending on the tissue’s resistance.
Duration: The shock duration is brief, lasting only a few milliseconds.
These shocks are designed to depolarize the cardiac muscle all at once, halting the chaotic electrical activity causing the arrhythmia and allowing the heart’s normal rhythm to resume.
