The term "Triplets" usually refers to 3 consecutive Premature Vebtricular Contractions or PVC's. In rare occasions they may report weakness, dizziness, or fainting. This is because frequent premature ventricular contractions can diminish the ability of the heart to pump blood to the other organs, resulting in low blood pressure. Patients with three or more consecutive premature ventricular contractions in a row have ventricular tachycardia. Ventricular tachycardia that is prolonged can result in low cardiac output, low blood pressure, and fainting. When I'm exhausted, I ofen begin to throw a single PVC here and there. A good night's sleep, and they disappear.
I would think it's referring to either premature atril beats (PACs) or premature ventricular contractions (PVCs). You would be getting 3 in a row to have a "triplet". Both of these are extremely common arrythmias and can be exacerbated by fatigue and stress.