The myofibrils of the dorsal vessel are arranged almost exclusively in an anterior-posterior orientation in tinABD ; tin346/tinEC40 larvae, in contrast to wild-type larvae where they are arranged spirally. In the posterior heart region of the dorsal vessel the pattern of myofibrils is highly irregular in the mutant larvae, forming abnormal cross-shaped or 'knotted' patterns. The aorta appears thinner than normal in the mutant larvae, whereas the heart frequently has a wider diameter than normal.

The heart tube is much thinner than normal in tinABD ; tin346/tinEC40 adults. The mutant myofibrils are arranged longitudinally and transverse spirally arranged myofibrils are almost completely absent.

tinABD ; tinABD tin346/tinEC40 adults show a dramatic increase in heart failure rate after pacing of the heart by external electrical stimulus compared to the heart failure rate of control adults. The recovery rate after heart failure is dramatically decreased in the mutant adults.

tinABD ; tinABD tin346/tinEC40 adults have a reduced lifespan compared to controls.