Can lowering blood pressure be a bad thing?

This study examined whether there was a link between low diastolic blood pressure (DBP) and the frequency of angina in patients with coronary artery disease (CAD; heart disease caused by a low blood supply to the heart because of hardened and narrowed blood vessels). The authors concluded that low DBP is associated with an increased risk of angina in these patients.

Reducing blood pressure (BP) in patients with hypertension (high blood pressure) helps reduce the risk of cardiovascular (heart and blood vessels) events. The optimal BP range, however, is unclear. 

There are two types of BP that are measured. Systolic BP (SBP) refers to the pressure in the blood vessels when the heart beats. Diastolic BP (DBP) refers to the pressure in the blood vessels when the heart rests between beats. Reducing BP too much can have negative effects however and aggressively treating DBP can actually increase the risk of heart attacks. There is very limited information looking at DBP and angina (chest pain caused by reduced blood flow to the heart). It is possible that reducing DBP too much can actually increase the frequency of angina.

The study included 1259 patients with CAD. Of these, 33% of patients reported at least 1 episode of angina within the last month. 79.7% of patients had been diagnosed with hypertension and were on BP-lowering medication. The authors measured the frequency of angina according to DBP.

The authors found that lower DBP was associated with a higher frequency of angina. Patients who had a DBP of 60 mmHg had a 37% higher risk of angina compared to those with a DBP of 80 mmHg.

The authors concluded that in patients with CAD, there was an association between lower DBP and an increased frequency of angina. They state that doctors should be cautious with aggressive BP control treatment in patients with CAD.

Patients on treatment for angina can be treated with medication that sometimes results in lowering DBP. This was not fully taken into account in this study. Also, the medication dosage was not included. There was only one measurement of DBP over a 4 week period. Further studies are needed to confirm these findings.

Talk to your doctor if your DBP is too low.