Coronary Artery Calcium Scans Detect Early Stages of CAD

Cardiovascular disease is the leading cause of death in men and women in the United States. Approximately 50% of acute myocardial infarction’s occur in people without any history of coronary artery disease. Sudden cardiac death is often the first sign of coronary heart disease. Coronary atherosclerosis is a slow progressive disease that oftentimes goes unrecognized … Continue reading “Coronary Artery Calcium Scans Detect Early Stages of CAD”

Cardiovascular disease is the leading cause of death in men and women in the United States. Approximately 50% of acute myocardial infarction’s occur in people without any history of coronary artery disease. Sudden cardiac death is often the first sign of coronary heart disease. Coronary atherosclerosis is a slow progressive disease that oftentimes goes unrecognized until the person develops symptoms. By the time symptoms start to occur coronary artery disease is usually in a relatively advanced stage requiring either percutaneous or surgical revascularization. The opportunity for disease prevention or aggressive risk factor modification is missed. What is needed is a way to identify asymptomatic people who are at high risk for cardiovascular events early in their disease process. Traditional cardiovascular risk factors are well established (elevated lipid levels, hypertension, smoking, obesity, lack of exercise, diabetes, family history heart disease) and helpful to predict future cardiovascular disease. Many people however suffer cardiovascular events in the absence of these established coronary artery disease risk factors.

Myocardial infarctions usually occur in patients who have a mild of moderate coronary artery stenosis that develops plaque rupture and leads to an acute thrombosis. These mild to moderate coronary lesions may not cause symptoms and/or may not cause enough ischemia to be picked up during a routine stress test.

During the early stages of coronary atherosclerosis calcium starts to accumulate within the plaque. As the atherosclerotic process progresses the amount of calcification increases. During the advanced stages of atherosclerosis a large amount of coronary calcification may be present.

Women have been reported to have less coronary artery calcification than men and the mean prevalence of calcification in women occurs about one decade later than in men, as does the incidence of cardiovascular events. The prevalence of calcium in adults 30 to 39 years of age is 21% for men and 11% for women, while in adults 40 to 49 years of age the prevalence is 44% in men and 23% in women. A recent study found coronary calcium scores were similar in African American and Caucasian women even though African American women had more risk factors. Diabetes mellitus and not exercising regularly was associated with increased Coronary Artery Calcium Scores in white women but not African American women. The overall prevalence of calcium in women is about half that of men until age sixty. Another study in asymptomatic women found that smoking, elevated total cholesterol levels, and hypertension were all associated with higher Coronary Artery Calcium Scores. Calcium deposits have also been found to increase with age irrespective of gender. Patients with diabetes and patients with end stage renal disease requiring hemodialysis have a higher prevalence of calcium. The more cardiovascular risk factors a person has the higher the prevalence of calcium.

Atherosclerosis is the only disease process known to cause calcium to deposit in coronary artery walls. Calcification is not a degenerative disease, it is not a part of the “normal” aging process. Calcium is not found in normal coronary arteries.

Since calcium deposits start to develop during the early stages of atherosclerosis and if we are able to identify the presence of calcium we are able to identify preclinical coronary artery disease during the asymptomatic stage. This can allow for the implementation of early aggressive risk factor reduction.

The calcium score screening heart scan is a non-invasive test that detects calcium deposits in the coronary artery walls. The test is performed with an electron beam cat scanner (EBCT) that permits very rapid scanning. The images are triggered with the assistance of ECG monitoring during diastole and a several second breath hold to eliminate motion artifact. The actual scan only takes about thirty seconds and computer software then quantifies the calcium area and density.

The EBCT detects the presence, location and extent of calcium deposits in the coronary system. Separate calcium scores may be obtained for the left main artery, left anterior descending artery, left circumflex, and right coronary artery but the total calcium score is most important. The EBCT can detect minuscule calcium deposits which is what is usually present with early coronary artery disease. The presence of any coronary calcification signifies coronary artery disease. People with low total calcium scores are at a lower cardiovascular risk than high scores.

Calcium scores range from zero (no plaque) to several thousand (extensive plaque) and is a unitless measurement calculated for the entire coronary system. A calcium score of zero indicates the absence of any calcium and an extremely low likelihood of obstructive coronary artery disease. A calcium score greater than 400 signifies extensive calcification and a high likelihood of significant coronary artery disease. (See Average Calcium Score Chart) These people should undergo further evaluation with exercise stress test or nuclear stress test for myocardial ischemia. The higher the total score the greater the overall plaque burden. Asymptomatic people with an intermediate calcium score require a thorough risk assessment and individualized risk factor modification. A person’s age and gender also need to be considered when evaluating the calcium score results. A calcium score of 175 may be average for a 65 year old male but grossly abnormal for a 55 year old female.

The calcium scoring scan is not able to identify the location of a significant coronary artery lesion nor identify the percent stenosis. The quantity of coronary artery calcium predicts the total atherosclerotic plaque mass and likelihood of developing future cardiovascular events. Coronary calcium has been reported to be an independent predictor of stable angina, myocardial infarction, cardiovascular death, and need for coronary revascularization. A study in asymptomatic adults 20 to 69 years old found that at 18 month follow-up the myocardial infarction and cardiovascular death rate was 6.6% in people who had any calcium present on scan versus 0.9% in people without any calcium. There is a direct relationship between increasing calcium scores and the occurrence of adverse events. Asymptomatic people with very high calcium scores (> 1,000) have been found to have an approximately 25% risk per year of developing a myocardial infarction of cardiovascular death. A recent study of asymptomatic adults over 45 years of age with at least one cardiovascular risk factor found a fourfold increase in cardiovascular risk in patients with coronary artery calcium scores greater than 300. A study performed on symptomatic patients found that a coronary artery calcium score greater than 170 was associated with an increased likelihood of obstructive coronary artery disease regardless of the number of risk factors present.

A recent meta-analysis reported a 92.3% sensitivity and 51.2% specificity for the accuracy of the EBCT to diagnose obstructive coronary artery disease. This makes the overall predictive accuracy approximately 70%. One advantage of the scan is there are no “false positive” scans, calcium deposits are only found in the presence of plaque. Interscan reliability of calcium scores has been questioned and has been reported to vary more with lower score. One study reported a calcium score variability of 28% in women and 43% in men when repeat scans were performed on the same individual. This really needs to be evaluated further and may be dependent on the facility, equipment of physician interpreting the results.

Non-calcified, soft plaques will not be detected by EBCT. Younger patients who are heavy smokers may not have calcium deposits present but are still at high cardiovascular risk and prone to spasm and thrombus formation. There has been some research to suggest that patients with unstable angina are prone to have fewer calcified plaques than patients with stable angina. Younger patients may develop a significant stenosis in the absence of calcification. This may falsely reassure people who are at high risk. There is not enough data to support using the coronary calcium scans in symptomatic patients of patients already know to be at high risk.

The coronary calcium scan (EBCT) is most useful in asymptomatic patients with intermediate risk, to help determine the need for aggressive risk factor management. (See Coronary Artery Calcium Scans chart below)

Traditional non-invasive tests to evaluate coronary artery disease (exercise stress test, nuclear scans, stress echocardiography) only detect coronary lesions that are severe enough to limit blood flow and cause myocardial ischemia. People with very mild coronary artery disease or early atherosclerosis will not be identified. Coronary calcium screening is able to identify non-obstructive mild coronary artery lesions before symptoms develop. Asymptomatic people with high calcium scores are also more likely to have abnormal nuclear stress tests indicative of silent ischemia. In one study 46% of patients with coronary artery calcium scores greater than 400 had an abnormal nuclear scan while 0% of patients with coronary artery calcium scores less than 10 had an abnormal nuclear scan.

EBCT scans may proved to be more beneficial for screening women. Many times women present with atypical symptoms and are more likely to have false positive exercise stress tests and/or nuclear scans. Calcium scoring scans have been reported to have a higher predictive value for significant coronary artery disease in women and less false positives than men. The negative predictive value in one study of symptomatic patients was 96% in women and 89% in men. Women with normal lipid levels are also more likely to experience angina/myocardial infarction than men. The standard lipid profile does not always adequately reflect a woman’s cardiovascular risk. A study of asymptomatic women over 55 years of age with normal lipid levels found elevated coronary artery calcium score. This is an area that needs to be evaluated further but suggests that coronary artery calcium scores may prove to be very beneficial in assessing cardiovascular risk profiles in women.

Indications for Coronary Artery Calcium Scans:
1. Family history heart disease (especially premature heart disease)
2. History of smoking
3. Hypertension
4. Obesity
5. Elevated lipid levels
6. Diabetes
7. Men over 40 years old or postmenopausal women
8. Young people with atypical symptoms

Contraindications for Coronary Artery Calcium Scans:
1. Known coronary artery disease
2. People over 70 years old (little clinical benefit)
3. Pregnant women
4. Arrhythmias (Chronic atrial fibrillation, resting tachycardia – heart rate greater than 90 bpm) will
compromise image quality

Average Calcium Scores:
Men

74 years old 521

Women

74 years old 149

Energy Efficient Construction Gains Ground

My Uncle Dave Wakefield lives in Anchorage, Alaska in a tiny house built when efficiency meant minimal construction cost and square footage.

The house, which he’s lived in the past two decades, has changed little since its construction sometime before or during World War II. It has 2-by-4 walls, low ceilings, tiny rooms and a draftiness consistent with old homes built by homeowners who used whatever was lying around. In this case it probably meant surplus wood from nearby Elmendorf Air Force Base.

When I called Dave recently, he expressed happiness that the winter temperature had finally risen. “The high was 4 degrees today, and it feels almost tropical,” he said.

Turning up the heat

Tropical is relative. Dave said deep cold slammed them hard the week before.

Dave keeps the furnace cranked. But because so much of the heat leaks through the attic, walls and windows, massive icicles form, looking like clear, pristine stalactites. Hardly energy efficient.

Ironically, his house is green.

Building goes green

Construction methods certainly have changed since Dave’s house was built. In fact, better windows and thicker walls are the norm. The move to energy efficiency can be seen in the latest from the U.S. Green Building Council, which released its 2011 list of top 10 states for LEED-certified commercial and institutional green buildings per capita. The list is based on the U.S. 2010 Census.

Alaska didn’t make the cut, and Dave’s house certainly didn’t help.

However, the little house on Third Avenue across from the site of the old Native Hospital does provide an example of the importance of using techniques to improve efficiency in the nation’s homes, commercial structures and institutional buildings.

Efforts grow to improve construction

Buildings consume about 40 percent of the overall energy and 70 percent of the electricity in the United States, according to the National Renewable Energy Laboratory. Many efforts, including the Leadership in Energy and Environmental Design, or LEED, ratings system, are under way to reduce that and in the process lower production of greenhouse gases.

At the top USGBC’s list is Washington, D.C., which completed about 19 million square feet of LEED-certified space for a whopping 31 square feet per person in 2011. Colorado takes the No. 2 spot with 2.74 square feet per person, followed by Illinois, Virginia and Washington state.

California stands at No. 8 in the per capita ranking but scored first with total square footage at about 71.6 million. New York was second in overall square footage with 36.5 million.

People matter most

“Looking past the bricks and mortar, people are at the heart of what buildings are all about,” said Rick Fedrizzi, president and CEO of USGBC, in a statement. “Examining the per capita value of LEED square footage in these states allows us to focus on what matters most — the human element of green buildings.”

LEED certification, one of a number of ratings systems, measures site development, water savings, energy efficiency, materials selection and indoor environmental quality.”

LEED and other efforts — such as the net-zero, whole house and passive house movements — promote construction and retrofit practices that save long-term operational costs. Frequently, the measures can be paid off quickly and even then only add marginally to the overall cost of construction or remodel.

Reducing energy consumption

An NREL report, “Zero Energy Buildings,” says “energy consumption in the commercial building sector will continue to increase until buildings can be designed to produce enough energy to offset the growing energy demand of these buildings.”

Awareness of the value of energy and other efficiencies is gaining recognition. Corporations are embracing sustainability, consumers have begun to recognize the importance of using technology to manage their electricity use and utilities across the country are finding ways to help stakeholders use less so they can delay adding generating capacity.

Passive house

In northeast Ohio, the Cleveland Museum of Natural History recently completed a passive house for its Climate Change exhibit. The 2,500-square-foot, 3-bedroom, 2 1/2 bath home “assembles some of the world’s greenest technological advancements and packages it in a super-insulated shell,” writes Marc Lefkowitz for GreenCityBlueLake Institute, which is the center for sustainability at the museum.

The house, one of the first in the region, is so well insulated, so weather tight and so efficient that it will need no furnace.

Going net zero

Although few buildings can claim net-zero energy consumption status, more are on the horizon. A study from a Boulder, Colo.-based research firm says the net-zero world market, currently measured at a relatively small $225 million, is “set to explode,” growing to $1.3 trillion by 2035.

The chief cause cited is the European Union’s introduction of net-zero building codes at the end of the decade. Pike says the EU’s commercial and residential construction will account for about 90 percent of the total.

The North American market, meanwhile, would grow incrementally, researchers predict.

Home batteries

Of course, everything depends on energy prices, political climate and consumer mood. Katie Fehrenbacher of gigaom.com writes that Japanese consumer electronics giant Kyocera is working to package its solar collectors and energy management systems with lithium ion home battery systems from developer Nichicon Corp.

Fehrenbacher writes: “Kyocera says there’s been a growing demand for Japanese homes to be able to generate and store their own power following the earthquake, tsunami and nuclear disasters last year.”

Who knew that smart phones would take as much computing capability as they have? Who seriously predicted clean energy getting as far technologically as it has and preparing to challenge fossil fuels on their own terms. So why should we not allow the possibility for energy independent homes?

Solar Decathlon housing

In fall 2013, 20 teams that know all about the subject will unleash their creativity. They hail from colleges and universities across the country and will unveil the next generation of technological advancements, building and design techniques and energy efficiencies for home building in the U.S. Department of Energy’s Solar Decathlon.

The site for the biennial event will be on the West Coast this time around, at Orange County Great Park in Irvine, Calif. Since 2002, it’s been held on the National Mall in Washington, D.C. Teams have two years to build solar-powered, energy-efficient homes that are supposed to “combine affordability, consumer appeal and design excellence.”

Energy Secretary Steven Chu says the Solar Decathlon will “unleash the ingenuity, creativity, and drive from these talented students to demonstrate new ideas for how families and businesses can reduce energy use and save money with clean energy products and efficient building design.”

WaterShed winner

In 2011, the University of Maryland won with its WaterShed entry. The home had a “split butterfly roofline” that managed storm water, filtered pollutants from greywater and minimized water use. Solar, tight construction and efficient mechanical systems reduced energy use.

I’d love to unleash such a team on my Uncle Dave’s house. Actually, the best idea would involve an excavator and a dump truck and building fresh. Dave lives on a fixed income and pinches pennies to get by. Reduce his heating costs by 90 percent and he’d feel rich.

And he’d no longer have icicles that could kill a wandering moose.

Zero Day Attacks

What you need to know to protect your computer

In 2010, a sophisticated virus was discovered on computers that were part of the network controlling uranium enrichment plants in Iran. The virus, eventually named Stuxnet, had been designed to destroy physical assets. This was the first time that a malicious virus had been created, not to steal data, but to physically damage equipment that was controlled by a computer network.

Regin Malware

What is not well known about Stuxnet is that it used a total of five, zero day exploits to replicate and spread itself through the computer network. The exploits are simply code that has been designed to attack computer software through previously unknown vulnerabilities.

Because zero day attacks are aimed at unknown vulnerabilities, there is no way to protect a computer or network from them. Hackers and cyber-criminals discover these vulnerabilities and develop zero day exploits to attack a computer system. Once they have gained access, they can insert a virus or Trojan horse into the now compromised system.

In addition to the criminal uses, governments and the military use zero day exploits to sabotage or perform surveillance on an enemy. The use of Stuxnet against the Iranian nuclear program was such a program carried out by the government of the United States.

With the success of Stuxnet, zero day exploits have become big business. Governments, underground hackers and even talented amateurs are searching out and cataloging zero day exploits and selling them to the highest bidder. Whether that buyer is a government or a criminal organization, they have access to an undetected and undetectable way to compromise a computer system’s security.

That is what makes the zero day attacks so terrifying to large corporations, banks and government agencies. Stuxnet showed what could happen by using a zero day exploit to cause physical damage. If zero day attacks are unleashed against large commercial targets, the damage could easily run into the billions of dollars and there is no way to stop it.

On the other end of the spectrum, exploited webpages that download malware to your system or infected word or adobe documents can all be considered zero day vulnerabilities before they are discovered and fixed. These sites or documents exploit a vulnerability on your system and are fairly common, but tend to have random results. Targeting companies or organizations using these types of attacks is inefficient and easily stopped.

In 2010, there were a total of fourteen zero day vulnerabilities documented by Symantec throughout the world. The period between 2006 and 2011 saw a total of 71 incidents that met Symantec’s criteria. Although this may seem like a small number of exploits, each of them leads to an attack on a computer system or network.

Zero day exploits that target major organizations are thankfully rare, but can cause considerable damage when they get through. A year ago a zero day vulnerability was discovered on a politically important website. Although Microsoft had identified the exploit before it was imbedded, the patch had not been issued. The malware was linked to Chinese cyber-espionage agents and was targeted at visitors who were interested in national and international security policy. Microsoft quickly updated its malware protection.

Renewed calls for protection of our country’s power grid and critical industries demonstrate that the government is taking the possibility of new zero day attacks emerging seriously. The Department of Homeland Security (DHS), tasked with defending US nation’s infrastructure, has struggled with keeping up with technical advances and have not proven themselves effective in this role.

The commercial sector, unfortunately, has not fared much better. The threat landscape for large enterprises includes well-funded efforts at cyber-crime, including the attack on JPMorgan by Russian hackers earlier this year. Criminal or state backed efforts aimed at stealing intellectual or physical property are challenges that will only increase in the coming years as more of these zero day vulnerabilities are discovered and exploited.

Commercially, this makes a CIOs job a living nightmare. Until now, ensuring availability and controlling costs have been the largest challenges facing technical departments. Equal attention needs to be paid to providing security for their network against an unknown enemy who will be using an undetectable tool that can exploit an unstoppable vulnerability. The only good thing about zero day vulnerabilities is the short window that they are usually active. Once discovered, the lifespan of a zero day vulnerability is measured in the length of time before your next security update.

Ali Bitazar is Well-known Network Security Expert