Whats the best test for heart disease?

whats the best test for heart disease? can heart disease go undiagnosed or be missed by some tests? Ive had EKGs, A holter moniter, multiple stress test, echocardiograms, and even a cardiac MRI with contrast with no serious results
that would point to structural heart disease (on paper at least). physicially i am very unwell, palpuations, dizzyness, inability to exercise and rapid heart rate everyday. the only thing the docs notice is my sinus tachycardia but they don't know why its happening. any other tests I should get? all answers appriciated. god bless.