You’re in the middle of a disaster or on a long hike, and suddenly you feel a little faint. Or maybe you feel butterflies in your chest.
You check your pulse, and it’s going really fast. Since your pulse is an extension of your heart, that means you have a really fast heart rate also. What do you do?
Until you can get medical help:
1. Sit down if you can.
2. Check your pulse rate. (See the “Check Your Normal” insert below.) If it’s going at a speed of 100–110, and it’s at a regular rate (maybe a few skips) you could be just overtired or nervous. Sit or lie there for a few minutes and try to relax. Dehydration, fever, and anemia can cause the heart to beat fast like this also.
If the heart rate is closer to 150 or higher, you’re probably in what we call supraventricular tachycardia (SVT). In SVT, your heart’s electrical system, which controls the heart rate, gets out of kilter. (See the insert about the electrical system below.) This can result in two things.
First, when the rate’s that fast, the heart can’t efficiently empty the blood from its chambers. Second, those chambers’ pumping rhythms can get out of sync. (Normally your atria pump blood to your ventricles, which pump it out milliseconds later. You can hear that when you listen through a stethoscope. Tadump, tadump. That system can get out of whack in SVT.)
The Heart’s Electrical System
Normally the heart rate is triggered at the “sinus,” or “sinoatrial,” node (1). The impulse then travels through the heart, syncing the beats of the four chambers (atria and ventricles). The sinus node knows when to speed up or slow down the rate if it thinks the body needs more or less blood to furnish its needs.
Sometimes, for various reasons, the “supraventricular node” (2) can take over. It will trigger the heart to beat around 150 times per minute (supraventricular tachycardia—SVT). This is an abnormal rate and always too fast.
Occasionally, the left ventricle (7) can take over the rate at around 300 beats per minute (ventricular tachycardia—VT). That rate is unsustainable for life. If VT happens, you can try a hard thump with your fist to the middle of the chest, or hope the vagal maneuvers work. Neither method works very often, and if you can’t make it to a medical facility quickly, you’re likely not to survive.
(Ignore the other numbers in the picture for our purposes.)
Any of this is a big stress on the heart. Your blood pressure may drop because your heart isn’t pumping blood out as efficiently. If you have underlying heart disease you could have a heart attack.
Causes for SVT include thyroid disease, prescription medications, smoking, anxiety, recreational drugs, and a condition called Wolff-Parkinson-White syndrome (a slight electrical system abnormality you’re born with). Often, though, the cause remains unknown.
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3. If you think it’s SVT, get your heart rate down. Until you can get medical help there are a few things you can try to kick it back into a normal, safer, more-efficient rate. All of these stimulate your vagus nerve (which has direct connections to your heart) and help control the rhythm. After each “vagal maneuver,” check the pulse to see if your heart rate has slowed.
a. Valsalva maneuver.
Hold your breath and bear down in a strain (like if you’re constipated and straining to have a bowel movement). Do this for five seconds, then breathe. This changes the pressure in your chest and therefore in the big blood vessels in it. That fools your body into thinking your heart should slow down. If the pulse hasn’t slowed, try again. Another way to do the Valsalva maneuver is to stick a finger in your throat and gag yourself.
b. Carotid maneuver.
Find your carotid pulse (see top photo) just below your jaw. The vagus nerve runs next to it. Massage very firmly for five seconds. Warning: In rare cases this could knock off a piece of a blood clot lodged in this area and cause a stroke. Don’t do this in elderly people or anyone with a history of a stroke.
c. Ice-water facial.
A little odd, I know, but if you have cold water (preferably ice water,) dip your face in it a few seconds. This stimulates your vagus nerve to slow your heart by causing what’s known as the dive reflex. It’s the same reflex that helps some people survive for a long time under cold water by slowing the body’s metabolism down.
Whether or not one of these things works, or your heart rate converts back to normal on its own, get checked by a doc as soon as you can. SVT can also be prevented with prescriptions medicines.
Check Your Normal
Go ahead and check your pulse now. Yes, right now. If you know where to find it and what a normal pulse feels like, it’s going to be lot easier to check it when it’s abnormal. See the photos (right and top) to locate two of the most common areas.
Notice the regular rhythm, speed, and force of your normal pulse. If you have a watch, count the rate for ten seconds and multiply times six for the heart rate per minute. Or check the rate for fifteen seconds and multiply times four. The normal rate is 60–100 beats per minute. Some athletes may have slower normal rates because their heart pumps blood so efficiently.
Then check your pulse without counting to get a feel of what a normal rate is so that if you don’t have a watch when you need it, you can discern when it’s beating way too fast.
Carotid artery photo by Shannan Muskopf on Flickr. Illustration of the heart’s electrical system by J. Heuser, based on an illustration by Patrick J. Lynch, illustrator, and C. Carl Jaffe, MD, cardiologist, Yale University Center for Advanced Instructional Media. The illustration (only) is licensed under the Creative Commons Attribution 2.5 Generic license.