SVTS

Did four calls in the city, a maternity, a foster child who called the ambulance because she had a cold, and two SVTs.

An SVT is a supraventricular tackycardia -- a heart rate above 150 usually caused by a defect in the heart as opposed to someone's heart just racing because they ran a race. It's a great call from a medic's point of view because you can usually break it with one of the drugs you carry, and cure the patient -- at least for the time being right on the spot.

The first call was a guy living in a grungy apartment by himself in the north end. The call came in for chest pain. When we got there, the fire guys said his vitals were fine and he just wasn't feeling well. In my routine of late, I usually just look at the patient, feel their forehead and listen to their lungs before deciding how to get them to the ambulance -- walk or carry. I rarely feel the pulse unless the patient particuarly warrants it. I check it in the ambulance where I gennerally work the patient up. The guy's forehead was slightly diaphoretic, his lungs were clear, and the fire guys said his pulse was 80. I was going to see if the man could walk, but then he said the pain in his chest was like a pressure. That statement always buys a stair chair. But when I told my partner to get the stair chair, the patient said he didn't want to go to the hospital. I said, let me at least put you on the monitor and see what we see.

I popped him on it and whooa, he's banging away at 170. Nice and regular -- an SVT. There's the problem.

The drug of choice is adenosine, a short acting drug that stops the heart briefly and resets it. In the heart electricity travels from the SA node in the atrium, through the AV node, which is the gateway to the ventricles. The electricity, which causes the heart to contract, pauses briefly in the AV node to allow the atrium to contract first, pumping blood down into the ventricles, which then contract as the electricity comes through the AV node door. In an SVT, the AV node often acts more like a spinning revolving door then a straight one way door. The electricity whirls around causing the atrium and the ventricle to beat increadibly fast, thus causing the symptoms that cause the patient to call 911. The symptoms usually are just an uncomfortable feeling in the chest. Adenosine basically puts a stake in the revolving door, and just shuts down the AV node for a moment, hopefully allowing the heart to rest itself, restoring the natural one way flow of the electricity.

I got an IV in a vein in the man's AC -- the crook of the elbow, the prefered site to administer adenosine, and gave him six of Adenosine. Unfortunately, we just started getting our adenosine packaged in prefilled needleless syringes, so I gave the adenosine, then tried to follow it with a saline flush, but it took me too long to detach the prefilled syringe and hook up the line. My partner had the saline line shut off, so the adenosine didn't get the rocket boost it needs to get to the heart before its half-life ran out. I told the guy I had to give him another dose, and then he got all mad and started saying he wasn't going to have me experimenting on him. This preceeded a lengthy back and forth of me saying, you really need this, and him saying no you don't, and me saying yes you do, which ended up with me pushing the drug during a moment of his hesitation in countering my arguement, and it worked and he felt better. He still didn't want to go to the hospital, and we were there another twenty minutes trying to convince him. I had to call medical control and get it on the record that he didn't want to go. He said he would go to the VA the next day and I left him a copy of the before and after 12 leads, as well as a record of what I had done to show his doctor and he signed the refusal. Before we left he shook my hand and thanked me.

The very next call was for 21 year old with tachycardia. We found a fat 21 year old girl who had been out all night drinking. Again, the fire department gave me a set of vitals that were fine. I thought maybe the girl had the flu. When I asked her if she could walk to the hallway, she said, she was too tired to do that and that she had a history of SVT. I put her on the monitor and sure enough she's banging away at 228. I put a needle on the prefilled syringe, and loaded up another syringe with saline, stuck them both in the IV port and slammed them one after the other. She converted right away. She at least agreed to go to the hospital.

This link shows what an adenosine conversion looks like:

http://www.emedu.org/ecg/images/ans/2adeno_2a.jpg

You see the initial rapid rate, then the period of asystole or flat line, followed by some funky beats, then the regular rhythmn returns. The patient usually feels very uncomfortable during the brief interlude. The man got a headache. The girl, who had had adenosine several times before, didn't even realize I had given her the med. She just sort of gasped and said, "It just converted on its own." No, I just gave you the med, I said.

The other way to convert an SVT is with electicity -- shocking the patient at a lower level of electricity or joules than the shocking you see in the person in cardiac arrest -- at least for the initial dose. I have had some patients who have had both done, say they prefer the electricity to the uncomfortable feeling of the adenosine. I've seen both and would prefer the medicine.

The period of asystole usually is only a second or two, but I have seen it go as long as five or six seconds, which is more scary to the medic than the patient. I will try to post and old strip I have that shows a particuarly long conversion.