A recent study here has found that although all types of exercise improve blood vessel function after a heart attack, benefits disappear after you stop training.

After a month without any physical activity, endothelial function returned to baseline levels.  Long-term adherence to training programs is necessary to maintain vascular benefits on endothelial dysfunction.

The participants were randomized to aerobic training, resistance training, both combined, or no exercise for four weeks.

Flow-mediated dilation significantly improved in those who participated in all three exercise regimes.  It also improved in patients who did not exercise, but to a much lesser extent.

At baseline, flow-mediated dilation was about 4%, but after exercise, it increased to about 10% in all three exercise groups, whereas in those who didn't exercise, it only increased to about 5%.