No J-Curve Relationship Between BP and Death in Clinic Study

Marlene Busko

June 26, 2015

MILAN, ITALY — A real-world study of more than 4000 patients seen in a blood-pressure clinic did not find a J-shaped relationship in which patients with a low diastolic blood pressure were at increased risk of dying from all causes or from cardiovascular causes, researchers report[1]. Dr Stefanie Lip (University of Glasgow, Scotland) and colleagues examined 30-year mortality data from patients who attended the Glasgow Blood Pressure Clinic and had blood pressure determined after 2 to 5 years of antihypertensive treatment.

"In treated hypertensive patients, the diastolic blood-pressure J-curve is not apparent with achieved blood pressure 2 to 5 years from presentation," Lip reported, presenting the study at a late-breaking session at the European Society of Hypertension (ESH) 2015 Scientific Sessions. The researchers used a cutoff of 80 mm Hg (as opposed to 70 mm Hg) to define the group with the lowest diastolic blood pressure.

"One could argue that the J curve happens at lower diastolic [blood-pressure] levels," a member of the audience remarked. Lip conceded that perhaps they did not find a J-curve relationship because so few patients attained a diastolic blood pressure below 70 mm Hg after 2 to 5 years of treatment. Only 68 patients had a diastolic blood pressure <80 mm Hg with a systolic blood pressure >160 mm Hg, she noted.

Session cochair Dr Cristina Giannattasio (Milano-Bicocca University, Milan) said she had the same question and also wondered if the group looked at long-term coronary events as well as mortality. Lip acknowledged that they had looked only at hard outcomes.

To heartwire from Medscape, Giannattasio reiterated that the study has two problems. First, "normally we use the 70-mm-Hg value to determine if there is a J curve." Second, "patients have [cardiac] events; they don't [necessarily] die," so it would be interesting to have these data too, she said.

Is the J Curve a Real Phenomenon in a Real-World BP Clinic?

The diastolic blood-pressure J-curve phenomenon has been recognized since 1979, Lip explained. Since myocardial perfusion occurs only during diastole, if diastolic blood pressure is lowered, this can lead to cardiovascular events.

A recent study based on the Framingham Heart Study reported that people with isolated systolic hypertension and prior cardiovascular-disease events had an increased risk for recurrent CV-disease events if they had a diastolic blood pressure <70 mm Hg vs a diastolic blood pressure of 70 to 89 mm Hg[2].

Thus Lip and colleagues aimed to determine the practical implications of low diastolic blood pressure and its association with cardiovascular outcomes in treated hypertensive patients.

They identified 6072 hypertensive patients who were seen in their clinic and followed for 2 to 5 years. At their initial visit, the patients had a mean age of 53 years, a mean body mass index (BMI) of 27.6, and a mean blood pressure of 169/100 mm Hg. About half (52%) were women, about a quarter had prevalent cardiovascular disease, and a quarter had an estimated glomerular filtration rate (eGFR) <60 mL/min. About 60% drank more than six units of alcohol a week, and 44% were current or past smokers.

The researchers analyzed 30-year all-cause and cardiovascular mortality in 4491 patients with complete data. The patients were divided into nine blood-pressure categories, based on at least three readings taken after 2 to 5 years of treatment with antihypertensives.

Number of Patients in Nine Baseline Blood-Pressure Categories

Diastolic BP, mm Hg Systolic BP, mm Hg
  <140 140–160 >160
<80 271 182 68
80–100 824 620 218
>100 375 966 967

Of the 4491 patients, 521 patients (12%) had low diastolic blood pressure (<80 mm Hg).

With increasing systolic blood-pressure categories, fewer patients had low diastolic blood pressure: 18% of the patients with systolic blood pressure <140 mm Hg, 10% of patients with systolic blood pressure 140–160 mm Hg, and only 5% of patients with systolic blood pressure >160 mm Hg had a diastolic blood pressure <80 mm Hg.

Only 250 of 4491 patients (5.6%) had isolated systolic hypertension (blood pressure of >140/<80 mm Hg).

There was no J-curve relationship between diastolic blood pressure and either all-cause or cardiovascular mortality.

Compared with patients with a blood pressure of <140/<80 mm Hg (the reference group), patients with a blood pressure of 140–160/>100 mm Hg or a systolic blood pressure of >160 mm Hg had a significantly increased risk of 30-year all-cause mortality.

Similarly, compared with patients in the reference group, patients with a blood pressure of 140–160/>80 mm Hg or a systolic blood pressure of >160 mm Hg had a significantly increased risk of 30-year cardiovascular mortality.

Among patients with a low diastolic blood pressure, only those with a very high systolic blood pressure (>160 mm Hg) had an increased risk of all-cause and cardiovascular mortality, Lip pointed out.

Perhaps looking at blood pressures that were attained after longer than 5 years of treatment might reveal a larger number of patients with a diastolic blood pressure below 70 mm Hg, Lip speculated. In reply to another question, she said that they did not analyze the types of antihypertensives used by the patients.


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