Obesity Surgery and High Blood Pressure

Summarized by Robert W. Griffith, MD
April 24, 2006

Introduction

Bariatric surgery - surgery on the stomach to help fight obesity - has brought new hope to thousands of severely overweight people. We've discussed the known benefits - see the first link below - that include: marked weight loss, 'cure' of type 2 diabetes, lowered serum cholesterol, curing sleep apnea, and normalization of blood pressure. A new study has reported on the blood pressure benefits in more detail. The results are published in the Archives of Surgery, and we give a short summary of the findings here.

What was done

Because the results of a beneficial effect of bariatric surgery on blood pressure have not been well-defined in truly obese individuals, researchers from Pittsburgh decided to study this in patients with extreme obesity treated by Roux-en-Y gastroplasty (gastric bypass surgery) or gastric banding gastroplasty ¹.

Data were obtained by reviewing the medical charts of patients who had undergone bariatric surgery - most of them had Roux-en-Y gastroplasty, the others had vertical banded gastroplasty. The selected patients had to be over 18 with a body mass index (BMI) of 40 or greater, and to have had no previous surgery for obesity.

The information extracted from the records comprised, in the first instance, blood pressure ², BMI, and blood-pressure medication use.

What the results showed

There were 347 patient records selected for analysis - ¾ of them were women. Four out of 5 had Roux-en-Y and the rest had vertical banded gastroplasties. Half of each type were hypertensive (systolic pressure 140 mmHg or higher, diastolic pressure 90 mmHg or higher) before surgery; just over half of the hypertensives were being treated.

The BMIs of the Roux-en-Y patients averaged 56 and those of the vertical banding patients averaged 49 before surgery; after surgery the BMIs fell to about 35 in both groups over the next 18 months.

Overall, blood pressures were lower after surgery, with the diastolic being reduced more than the systolic. Different subgroups of patients provided further information:

• Patients with untreated high blood pressure had marked reductions in blood pressure - 16 mmHg (systolic) and 7 mmHg (diastolic), on average, 3 months after surgery.
• Hypertensive patients on medication had smaller decreases that the above.
• Systolic pressure in patients with normal blood pressure before surgery didn't decline, while there was a small (2 mmHg) reduction in diastolic pressure.
• Of 192 patients who were hypertensive, only 92 remained hypertensive after surgery.
• Of 103 patients taking antihypertensive medications, 35 were able to discontinue them after surgery without a recurrence of high pressure.

What do these findings mean?

The blood pressure changes seen after bariatric surgery clearly depend on the level of the blood pressure before surgery. If the patient has normal blood pressure, or is controlled by anti-hypertensive medication, the changes will be small. On the other hand, if the patient has high blood pressure that isn't treated (or controlled) by medication, a more substantial fall will occur.

A previous study along these lines, done in Sweden, found that the reduction in blood pressure after bariatric surgery was transient, and began to reverse after a year. There was no indication in the present study that the effect on blood pressure began to rise again once the lowest levels had been reached. However, the authors of the study are careful to warn that hypertension could re-emerge later.

What is the value of this study? Perhaps it's greatest value is to encourage obese hypertensives to take the plunge and have surgery, and to continue making the necessary dietary adjustments post-surgery. Reducing weight by other means is associated with improvements in elevated blood pressure, but the results of this study are more dramatic and, therefore, have a chance of being more convincing to the undecided.

Source

• Long-term changes in blood pressure in extremely obese patients who have undergone bariatric surgery FJD. Fernstrom , CAP. Courcoulas , HP. Houck , FMH. Fernstrom , , 2006, vol. Arch Surg, pp. 276--283

Footnotes
1. Roux-en-Y gastroplasty involves forming a small pouch (about egg-sized) from the stomach and joining this to the small intestine, so that the bulk of the stomach and the duodenum are bypassed. In vertical banded gastroplasty the upper stomach near the esophagus is stapled vertically to create a small pouch. The outlet from the pouch to the rest of the stomach is restricted by a band made of special material; this band delays the emptying of food from the pouch, causing a feeling of fullness.
2. Blood pressure readings are usually given as 2 numbers, e.g. 110 mmHg over 70 mmHg (written as 110/70). The first number is the systolic blood pressure reading, which represents the maximum pressure exerted when the heart contracts. The second number is the diastolic blood pressure, representing the pressure in the arteries when the heart is at rest.

Related Links
Get the Facts on Surgery for Obesity
Obesity and Hypertension: Two Epidemics or One?
Obesity Surgery and heart risk

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