The Long QT syndrome is an inherited disorder of the heart's electrical system that can cause sudden death, even in young, healthy individuals. Read about long QT syndrome, its causes and treatment, here.

Inappropriate sinus tachycardia (IST) is a condition in which an individual's resting heart rate is abnormally high (greater than 100 beats per minute), their heart rate increases rapidly with minimal exertion, and their rapid heart rate is accompanied by symptoms of palpitations, fatigue, and exercise intolerance. It is more common in women, and (while one hopes not) this may be why it is all too often written off by doctors as "anxiety." Read about IST, its causes and treatment, here.

Unstable angina is one of the types of "Acute Coronary Syndrome (ACS)," a series of conditions most commonly produced by the rupture of a plaque in a coronary artery. All types of ACS, including unstable angina, should be considered medical emergencies.

Unstable angina is "unstable" not only because a plaque has ruptured (a situation which always threatens to progress to a myocardial infarction), but also because the symptoms it produces - the angina - generally occurs much more frequently, often at rest, lasts much longer, and begins responding poorly to nitroglycerin.

Read more about unstable angina - how to recognize it and how it is treated - here.

On rare occasions, pregnancy can lead to a condition called postpartum cardiomyopathy, or pregnancy-associated heart failure.

Women who develop postpartum cardiomyopathy experience the onset of heart failure either during the last month of pregnancy, or within five months of delivering a baby. These women have no prior underlying heart disease, and no other identifiable reason to develop heart disease. Their heart failure can be a temporary, self-limited condition, or can progress to severe, life-threatening heart failure.

Read here about postpartum cardiomyopathy.