How significant is it on a stress echocardiogram that one cannot reach target heartbeat even at end of stage 3?

Protocol = ?: If bruce protocol, more fit person would make it to end of 4 or early stage 5 before hitting target hr. Usually interpretable as long as close to target (>85%) and images good.

Stress test: Multiple causes. Maybe you are on a beta blocker? This will prevent you reaching target rate. If you are really fit, your target rate may need more exertion. If your stress test was done for suspected coronary artery disease and you did not reach target, then information may be misleading. Talk with your doctor - if high risk for coronar artery disease, then condiser a chemical nuclear heart scan.

Not conclusive: For a stress test to be convlusive target heart rate should be achieved. If your target heart is not achieved with exercise then there are pharmacologic stress studies.