Ventricular refers to the bottom chambers of the heart, the right and left ventricles, as opposed to the top chambers, the right and left atria. Tachycardia refers to a fast heart rate. Typically, a tachycardic, or fast, heart rate is considered anything above 100 beats per minute, or bpm. However, ventricular tachycardia is different than a fast heart rate from exercising, which is called sinus tachycardia.
Normally, the electrical signals that generate each heartbeat start in the right atrium at the sinus node, which is also known as the sinoatrial node, or the SA node. If the rate goes over 100 bpm and originates in the SA node, it’s considered sinus tachycardia, which is totally normal.
However, heartbeats can become abnormal if the electrical signals don’t start in the SA node, but start in the ventricles instead. Premature Ventricular Contractions, or PVCs, are single beats originating from the lower chambers. Any time there are more than three beats like this in a row, then it’s defined as ventricular tachycardia. Ventricular tachycardia, sometimes called V-tach, or VT, can cause the heart rate to rise above 100 beats per minute, which can be extremely dangerous and lead to sudden cardiac death.
Hold on, how can that happen? It’s not like while we exercise we’re risking sudden cardiac death, right? Well, even though we say tachycardia is anything above 100 beats per minute, most patients with ventricular tachycardia experience heart rates as high as 250 beats per minute. 250 beats per minute mean that the heart is beating over four times per second. When the chambers are pumping that fast, they don’t have enough time to even fill with blood, so the heart is furiously pumping out only tablespoons of blood to your body, and most importantly, to your brain, which is just not enough. If this happens, a person can have symptoms from not having enough perfusion to their tissues, such as chest pain, fainting, dizziness, or shortness of breath. It can even cause sudden death.