If i'm a heart patient (with pacemaker/defibrillator), diabetic, can i take a natural thyroid supplement for my hypothyroidism?

No to "natural": If you are hypothyroid, you should take levothyroxine. So called "natural" thyroid is from slaughterhouse bovine thyroid, and contains a mixture of different thyroid hormones. The dose is not consistent, and it is harder for your doctor to follow and monitor. The consequences of hypo- or hyperthyroidism (from the pill) are much worse if you are diabetic and have heart problems.