Brief Answer:
Valsalva's maneuver is causing problem indirectly.

Detailed Answer:
Hi Dear,
Thanks for choosing HealthcareMagic for your query.As per your query answer is-

Frequency of bowel movements differs among different people and may also vary in every person’s bowel habits. While some people have bowel movements daily, sometimes even two to three times a day, other people may only do so once or twice a week. Constipation occurs when one’s bowel movements become less frequent than usual. When this happens after more than three days, it may be more difficult to pass stools because they become harder.

Difficulty in passing stools often leads an individual to strain while sitting on the toilet to pass stools forcefully. Straining involves holding one’s breath and bearing down. This action is medically known as a Valsalva’s maneuver, where one forcibly exhales against a closed glottis (a part of the airways involved in allowing air entry to the lungs).

During sustained straining while defecating, you are doing Valsalva maneuver, which increases abdominal pressure and helps in forcing out stools from the colon. However, this action also has effects on the circulatory system. Holding your breath while bearing down causes a temporary increase in pressure inside the chest, which reduces blood flow to the heart. Heart rate also decreases and during this period, the blood volume pumped by the heart to the rest of the body may fall. The body compensates with a series of increases and decreases in blood pressure and heart rate. As you release the straining motion and begins to breathe again, a sudden rise in arterial blood pressure and a slowing of heart rate may occur.

I hope you understood well the cause of your elevated blood pressure while defecating.
Basically its something physiological and not pathological.

Treatment-
Use any laxative like lactulose or Isabghul husk this will cause your stools to pass easily through your anus.
Things will settle down if constipation is relieved.

In case you have any other query please do follow up.

Regards!

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Brief Answer:
Follow up with advice.

Detailed Answer:
Hello again Dear,
As already explained by me above constipation is the root cause of all your problem.So take treatment for constipation and you will feel relieved.Treat the root cause of problem and problem would be solved.
Over straining is stimulating your nerves causing increase blood pressure.Take syrup lactulose daily to relieve you from constipation.There is no need to worry right now nut quality of life is compromised due to constipation.As diet changes alone are not sufficient you should take laxative.
Marked elevation of systolic blood pressure is suggestive of over stimulation of nervous system.

Hope i answered your query.
Regards.

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