Imran Khan suggest that the heart attach of Dr. Rizwan was due to some kind food poison. Although, there are chemical that cause heart attach, like cocaine and methamphetamine. However, by heart attack he probably meant cardiac arrest which is different than heart attack as below.
Heart Attack: Usually occurs due to blockage of blood vessels supplying blood to the heart called coronary arteries. In other words, it's related to the plumbing of the heart. If heart attack is not treated promptly, especially in young adults, then it can lead to cardiac arrest and death.
Cardiac Arrest: When heart beats irregularly and finally comes to a stand still. In other words, it's an electrical issue of the heart.
Difference between Heart Attack and Cardiac Arrest can be easier to understand when one compares a similar phenomenon in the brain as below.
Stroke (also called a Brain Attack) = Cardiac Arrest (it leads to death of that tissue that supplied by the blood vessel that is blocked)
Seizure (haphazard activity in the brain) = Ventricular Fibrillation which if not treated through a CPR/Shock will lead to the death.
Below is not an exhaustive list of Poisons that can lead to Cardiac Arrest (not Heart Attack).
Note: Some of these substances are used as medicine.
Difference between Medicine and Poison is that of the DOSE.
# Nicotine
Nicotine is a colorless, liquid alkaloid found in several species of tobacco plants. It is an extremely fast-acting poison. All parts of the plants are poisonous except the ripe seed. Nicotine is rapidly absorbed from all mucous membranes, skin and lungs.
1 cigarette = 15-20 mg nicotine of which 1-2 mg is absorbed by smoking.
Fatal Dose: 50-100 mg of nicotine
Fatal Period: 5 to 15 mins
# Aconite
Aconite is commonly known as monk’s hood, blue rocket, bish, bikh, sweet poison, or Devil’s helmet. Its common varieties are Aconitum napellus and Aconitum ferox. The plant Aconite is grown in garden and its flowers are grown in the Himalayan ranges in India. It has no odour, but is sweetish in taste hence the name Mitha Bish.
Fatal Dose of root is 1 gm and aconitine is 2 to 5 mg.
Fatal Period is 2 to 6 hrs.
# Quinine
Bark of numerous species of Cinchona plant contains quinine and cinchonidine. The medicinal use of quinine is the treatment of malaria.
Fatal Dose: 8 – 15 gm
Fatal Period: 6 hrs
# Reserpine
Reserpine is an alkaloid present in the root of the Indian plant Rauwolfia serpentina. It has been used for treating hypertension for decades.
It is readily absorbed through oral and intramuscular dosing.
# Potassium
This element is tightly controlled and can be quite deadly if ingested at high doses. However, at high doses the food can be quite unpalatable.