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Internally-driven, daily blood pressure cycle does not appear to be responsible for the known morning increase in cardiac events.
Blood Pressure's Internally-Driven Daily Rhythm Unlikely to Be Linked to Morning Heart Attacks
Study Highlights:
- The human body clock influences blood pressure independent of changes in environment and behavior.
- The internally-driven, daily blood pressure cycle does not appear to be responsible for the known morning increase in cardiac events.
- Volunteers on three different sleep cycles had almost identical internal blood pressure cycles, peaking at about 9 p.m.
- The reason for the peak in heart and stroke in morning hours remains unexplained.
DALLAS, April 7, 2011 /PRNewswire-USNewswire/ -- The internally-driven daily cycle of blood pressure changes doesn't appear to be linked to the known increase in morning heart attacks, according to a study in Circulation Research: Journal of the American Heart Association.
Researchers sought to identify the role of the internal human body clock in the daily rise and fall in blood pressure. In the study, three groups of volunteers showed an internal daily blood pressure variation with a peak at around 9 p.m. — independent of changes in activity and other behavioral influences that can affect blood pressure.
Increased blood pressure is a major risk factor for adverse cardiovascular events. However, the study revealed that the internal blood pressure cycle resulted in the lowest blood pressure occurring in the late morning. This unexpected finding indicates that blood pressure's internal circadian rhythm — a cycle of about 24 hours that occurs in many biological processes — is unlikely to be linked to the well-documented morning peak in heart events or strokes, said Steven A. Shea, Ph.D., lead author of the study and associate professor of medicine at Harvard Medical School in Boston, Mass.
"We used three complementary experimental protocols and three different groups and found essentially the same results," Shea said. "That means we're dealing with something very robust."
Shea and his colleagues randomized 28 volunteers without hypertension to three multi-day in-laboratory protocols. Before the study, participants maintained a regular sleep-wake schedule at home (16 hours of scheduled wakefulness with eight hours of scheduled sleep) for two to three weeks to stabilize circadian rhythms.
They then underwent two baseline days and nights in the laboratory with the same sleep-wake schedule as at home, followed by a prolonged laboratory protocol designed to separate internal circadian effects from behavioral and environmental effects on blood pressure and other physiological variables. These controlled behavioral and environmental conditions included activity, posture, meals, sleep, room temperature, and light.
The researchers measured core body temperature to track circadian time. The three protocols, carried out in dim light to avoid resetting any of the body's circadian rhythms, included:
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38-hour "constant routine," with continuous wakefulness and constant body posture.
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196-hour "forced desynchrony" (forcing a sleep/wake cycle to conflict with participants' normal pattern) consisting of recurring 28-hour sleep/wake cycles with 18 hours, 40 minutes awake and 9 hours, 20 minutes asleep.
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240-hour "forced desynchrony" with twelve recurring 20-hour sleep/wake cycles.
All three protocols revealed almost identical systolic and diastolic circadian rhythms, which were unrelated to other internal rhythms that are known to influence cardiovascular events, such as increases in sympathetic nervous system activity.
The reason for the peak in heart attacks and strokes in morning hours remains unexplained by these findings, but could certainly be related to the activities that normally occur on a regular daily basis. "For example, other recent work by our group indicates that the body clock interacts with behaviors, such as exercise, to cause an exaggerated increase in cardiovascular risk markers during the biological morning," adds Frank A. Scheer, Ph.D., co-author of the study and assistant professor of medicine at Harvard Medical School.
It is possible that the evening peak in the internal circadian blood pressure cycle may help to explain a second, albeit less prominent increase in heart attacks that occurs in the evening, the researchers said.
"We now need to study people with different vulnerabilities and risk factors for cardiovascular disease," Shea said. "So far, we have studied very healthy people who don't have hypertension or the build-up of arterial plaques that could bring them closer to the theoretical threshold for precipitating an adverse cardiac event."
Other co-authors are Michael F. Hilton, Ph.D.; Kun Hu, Ph.D.; and Frank A.J.L. Scheer, Ph.D. Author disclosures and funding are on the manuscript.
Statements and conclusions of study authors published in American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect the association's policy or position. The association makes no representation or guarantee as to their accuracy or reliability. The association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific association programs and events. The association has strict policies to prevent these relationships from influencing the science content.
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Highlights of Article by Dr. Erik Hess et of Mayo Clinic ;CIRCOUTCOMES 2012
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Chest pain is the 2nd most common reason patients come to EDs across the United States
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Initial testing – including information obtained from the history, physical exam, electrocardiogram, and cardiac troponin – identifies > 98% of heart attacks
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To avoid missing a diagnosis of heart attack or pre-heart attack symptoms, emergency physicians often admit patients to observation units or to the hospital for extensive diagnostic testing, including stress testing
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This results in false positive test results, unnecessary exposure to radiation, and unnecessary downstream procedures such as stent placement in arteries of the heart
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Decision aids are evidence-based tools designed to educate and engage patients in decisions regarding their care
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We hypothesized that patients who were educated regarding their future risk for a heart attack and engaged in the decision of whether to be admitted to the observation unit for stress testing or to follow-up with a Mayo Clinic heart doctor in the next 72 hours would have greater knowledge about their short-term risk for heart attack, be more aware of the management options, and choose less intensive approaches to evaluation
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We randomly assigned 204 patients who came to the ED with chest pain and were being considered for observation unit admission to the decision aid or to usual care
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Decision aid patients:
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Had greater knowledge regarding their short-term risk for a heart attack
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Less frequently decided to be admitted to the observation unit for stress testing
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Had 4 times greater engagement in the decision making process
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Had no adverse events within 30 days of the ED visit
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Take home points
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Patients want to be educated and engaged in decisions regarding their care
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Once properly informed and engaged in treatment decisions, patients often choose less intensive treatment options
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Integrated health systems like the Mayo Clinic in which physicians collaboratively work together to provide ER patients ready access to outpatient follow-up have potential to improve the value of Emergency care
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Glucose, Insulin and Potassium (“GIK”) TO MINIMIZE IMPACT OF HEART ATTACKS BEFORE PATIENTS GET TO THE HOSPITAL
Study puts life-saving drugs in the hands of paramedics, decreasing rate of cardiac arrest and death from heart attacks
CHICAGO (March 27, 2012) — Paramedics can potentially reduce someone’s chances of having a cardiac arrest or dying by 50 percent by immediately administering a mixture of glucose, insulin and potassium (“GIK”) to people having a heart attack, according to research presented today at the American College of Cardiology’s 61st Annual Scientific Session. The Scientific Session, the premier cardiovascular medical meeting, brings cardiovascular professionals together to further advances in the field.
The study showed that patients who received GIK immediately after being diagnosed with acute coronary syndrome — which indicates a possible heart attack is either in progress or on the way — were 50 percent less likely to have cardiac arrest (a condition in which the heart suddenly stops beating) or die than those who received a placebo, although the treatment did not prevent the heart attack from occurring. The reduction in in-hospital cardiac arrest or death was a “secondary endpoint”, so statistically was not definitive, but was consistent with how GIK seems to work in experimental models of heart attack.
The effect was also present for patients with ST-elevation heart attacks, which require immediate treatment. For those patients, immediate GIK was associated with a 60 percent reduction in in-hospital cardiac arrest or death.
“When started immediately in the home or on the way to the hospital — even before the diagnosis is completely established — GIK appears not completely prevent any heart attack from occurring, but appeared in this trial to reduce the size of heart attacks and to reduce by half the risk of having a cardiac arrest or dying,” said Harry P. Selker, MD, MSPH, executive director of the Institute for Clinical Research and Health Policy Studies at Tufts Medical Center, who led the study with Joni Beshansky, RN, MPH, co-principal investigator and project director. “Acute coronary syndromes represent the largest cause of death in this country. GIK is a very inexpensive treatment that appears to have promise in reducing those deaths and morbidity.”
The cost of the treatment is about $50.
“Because the trial is the first to show GIK could be effective when used by paramedics in real-world community settings, it could have important implications for the treatment of heart attacks,” Dr. Selker said. Previous clinical trials have shown no consistent effect, likely because the GIK was given too late to help. This study, the “IMMEDIATE Trial,” was the first to test the effectiveness of administering GIK at the very first signs of a threatening heart attack, in the community, rather than waiting hours until the diagnosis was well-established at a hospital, as done in previous clinical trials.
“We wanted to do something that is effective and can be used anywhere,” said Dr. Selker. “We’ve done a lot of studies of acute cardiac care in emergency departments and hospitals, but more people die of heart attacks outside the hospital than inside the hospital. Hundreds of thousands of people per year are dying out in the community; we wanted to direct our attention to those patients.”
The researchers trained paramedics in 36 Emergency Medical Services systems in 13 cities across the country to administer GIK after determining that a patient was likely having a threatened or already established heart attack using electrocardiograph-based ACI-TIPI (acute cardiac ischemia time-insensitive predictive instrument) and thrombolytic predictive instrument decision support that prints patient-specific predictions on the top of an electrocardiogram. The paramedics used these predictions to decide if a patient would likely benefit from treatment. There were 911 patients randomized to receive either the GIK treatment or a placebo.
Administering GIK immediately also reduced the severity of the damage to the heart tissue from the heart attack. On average, 2 percent of the heart tissue was destroyed by the heart attack in people receiving GIK, compared with 10 percent in those who received the placebo. Although a significant proportion of suspected heart attacks are later determined to be false alarms (23 percent in this study), administering GIK does not appear to cause any harmful effects in such patients.
The research team will follow up with study participants at six and 12 months to evaluate the longer-term benefit of the GIK treatment.
This study was funded by the NIH’s National Heart, Lung and Blood Institute.
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Amazon.com 's Editorial Reviews
Angina: New Ways to Treat
Chronic Chest Pain
Part of the award winning public television series Healthy head
/Healthy Mind. It's one of the scariest medical symptoms for people who are generally healthy: a tightening, painful feeling in the chest known as Angina. In some cases this chest pain can be a serious warning that requires immediate treatment. But for the millions of people with chronic, stable angina the discomfort is something that can be readily managed with a variety of treatments. In this program we take a look at what generally causes angina, what can be done to prevent it and how it can be effectively treated with lifestyle changes, innovative drug therapies and medical procedures.
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Amazon.com Editorial Review:
Philips HeartStart Home Defibrillator (AED)
Be prepared for the unexpected.
When sudden cardiac arrest (SCA) strikes, the electrical system of the heart short circuits, causing the heart to quiver rather than pump in a normal rhythm. It typically results in the abnormal heart rhythm know as ventricular fibrillation (VF). It usually happens without warning and the majority of people have no previously recognized symptoms of heart disease. And it most often happens at home. For the best chance of survival from SCA caused by VF, a defibrillator should be used within 5 minutes. Yet, less than 1 in 20 people survive largely because a defibrillator does not arrive in time.
Just as seat belts or airbags do not save every life in a traffic accident, a defibrillator will not save every person who suffers a sudden cardiac arrest. Yet many lives could be saved if more people could be reached more quickly.
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