Chinese medicine accounts for diurnal fluctuation in blood pressure, with something called the Horary Clock, which is the circadian cycle of Qi through the organ systems. The highest blood pressure occurs at mid-day; noon-time is indeed associated with the Heart according the Horary Clock.
"There are acupuncture protocols where the actual time of a treatment may be enhanced by coordination with the flow of Qi according to the Horary Clock. [Since] this is not always practical, organs opposite each other on the Horary clock will balance each other regardless of the time treated [i]. Mid-day (or the opposite time, 11 PM to 1AM) are good times for DIYs to benefit cardiovascular health.
For example napping for 1 hour between 11AM to 1PM (Heart time) nourishes the spiritual Heart (the Shen). Nurturing yourself and relationships then winding down for sleep between 7PM to 11PM (Pericardium and San jiao time) strengthens and rests the Heart. Sleeping well between 11PM to 1AM (Gallbladder time) restores the Heart. Staying up; complaints of insomnia, or not achieving deep sleep between 1AM to 3AM (Liver time) increases the risk for "deficiency Liver Fire Flaring", which is a pattern associated with hypertension in Chinese medicine.
See how to care for your Heart health according to the Horary Clock. (Do not take Kyushin Pills without a prescription from an Chinese herbal prescriber because studies show one of its herbal ingredient interacts with the cardiac drug called Digoxin).