Posts Tagged ‘sudden cardiac death’

Heart Rate Variability (HRV) as a Tool

Reporter and Curator: Larry H. Bernstein, MD, FCAP

The article that follows expands on the discussions about exercise, walking or running, and burning calories, an adjunct to good nutrition.  It elucidates how monitoring of performance in physical conditioning is done by monitoring the heart rate variability.  The fact is that outside of concussion injuries that may take a toll in time, or even cause a subdural hematoma, there are “silent” events that are related to sudden death.  These are serious cardiovascular events.

Heart Rate Variability (HRV) as a Tool for Diagnostic and Monitoring Performance in Sport and Physical Activities

Journal of Exercise Physiology  Jun 2013; 15(3):103-131.  ISSN 1097-9751

B Makivic, M Djordjevic, MS Willis

1Center for Sport Science and University Sport, University of Vienna, Vienna, Austria, 2Faculty of Sport and Physical Education, Belgrade, Serbia, 3McAllister Heart Institute, University of North Carolina, Medical Biomolecular Research Building, Chapel Hill, NC.

The dynamic autonomic responses during exercise can be measured

  • to give actionable information for training
  • by analysis of the ECG to determine heart rate variability (HRV).

While application of HRV has been applied to

  • predict sudden cardiac death and diabetic neuropathy
  • in assessing disease progression,

recent studies have suggested that it may be applied to exercise training. In this review, we present

  • the rationale for measuring HRV.

We describe the

  • different variables used and
  • what they can tell us about the autonomic nervous system.

The use of HRV in detecting changes in exercise intensity is presented, along with evidence that

  • gender and age changes may affect autonomic HRV.

Lastly, we illustrate how

  • HRV measurements taken immediately post-exercise have proven to be useful
  • in measuring and monitoring training load to proscribe workouts and/or prevent over-training.

Despite the studies that

  • vary widely in their application to different training levels of athletes being tested and
  • HRV measures used,

the standardization of methodologies and results should help accelerate the use of HRV in sports training.
Key Words: Autonomic Nervous System; Overtraining; HRV

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Reporter: Aviva Lev-Ari, PhD, RN


Postmortem MRI shows sudden cardiac death invisible at autopsy

By Eric Barnes, AuntMinnie.com staff writer
April 17, 2013

In results that add substantial forensic power to identifying the cause of death, postmortem cardiac 3-tesla MRI has been found to identify sudden cardiac death in cases that are invisible at conventional autopsy, according to new research published online in the Journal of the American College of Cardiology.

In 76 cases, unenhanced MRI was able to visualize and discriminate 124 myocardial lesions, and there was excellent correlation among autopsy findings on chronic, subacute, and acute cases at MRI, the study authors said.

Thus, 3-tesla MRI can visualize chronic, subacute, and acute myocardial infarction in situ, and shows a possible source for sudden cardiac death in peracute infarction, wrote Dr. Christian Jackowski from the University of Bern in Switzerland, along with colleagues from the University of Lausanne in Switzerland and Linköping University in Sweden.

In particular, peracute infarction findings cannot be replicated in a physical autopsy; therefore, the study findings supports the use of forensic autopsy by permitting targeted histology, the group reported. Thus, MRI may serve as an alternative postmortem examination technique to traditional autopsy, Jackowski and colleagues wrote (JACC, April 3, 2013).

“In forensics, the cases can be solved better and more convincingly,” Jackowski wrote in an email to AuntMinnie.com. “The second impact I see is for clinical pathology, which has suffered from declining autopsy rates for decades now. I don’t expect the clinical autopsy numbers to increase again, so postmortem MRI can provide information about the cause of death, especially in patients that do not undergo a clinical autopsy anymore.”

Most cardiac deaths remain unsolved

Considering that cardiac events account for most deaths, postmortem MRI’s ability to demonstrate the cause of death in the heart has an enormous potential benefit, the group wrote, noting that “tissue alterations occurring during and after myocardial ischemia” are the most important — yet the least understood — issue with regard to conventional autopsy.

In previous small studies, acute, subacute, and chronic infarction have been differentiated based on signal behavior in T1- and T2-weighted images. Previous research has also suggested that unenhanced T2-weighted images without a hyperintense margin may represent acute ischemic lesions, which are aged between about 15 minutes and one hour, the group noted. Generally, though, cases of sudden cardiac death without myocardial findings of fresh thrombus have puzzled examiners and pathologists for decades.

The study sought to validate previous findings using postmortem MRI at 1.5 tesla, and also sought to use a larger study population. A secondary goal was to link the MRI finding of T2-weighted myocardial hypointensity to the possible myocardial appearance of sudden death to the patient’s coronary status at autopsy. The group used 3-tesla MRI to examine 136 corpses whose case histories showed chronic or acute cardiac anamnesis, or death from circumstances suggesting a cardiac origin.

All cases were examined with MRI using acquired short-axis and horizontal long-axis imaging on a 3-tesla MRI system (Achieva, Philips Healthcare) using a 16-channel torso coil.

Peracute myocardial infarction in postmortem MRI

Peracute myocardial infarction in postmortem MRI (death within one hour). A T2-weighted short-axis image presents with a local hypointensity within the lateral wall without hyperintense edematous margin. Autopsy of the specimen showed no visible alteration within the affected myocardium (not shown). Histology also failed to demonstrate ischemic alterations (not shown). Dissection of the coronary artery system revealed a fresh soft-plaque rupture with intimal hemorrhage within the circumflex coronary artery (not shown). Image courtesy of Dr. Christian Jackowski.

A total of 76 cases (62 men, 14 women; mean age at death 57.8 ± 16.7) presented with cardiac findings at postmortem MRI were investigated further.

Findings of cloudy hypointense myocardial areas in T2-weighted images without any hyperintense marginal edematous reaction were diagnosed as peracute ischemic lesions, and were not visible at autopsy, Jackowski and colleagues wrote.

Among the 76 cases, postmortem analysis identified 124 myocardial lesions (chronic = 25, subacute = 16, acute = 30, and peracute = 53), the team wrote. They found excellent correlation among myocardial findings at autopsy and chronic, subacute, and acute infarction cases. Peracute infarction areas detected at postmortem MRI were verified by histology in 62.3% of cases, and could be related to a matching coronary finding in 84.9%, they wrote.

In 15.1% of peracute lesions seen at MRI, the researchers found no matching coronary finding. But these patients presented severe myocardial hypertrophy or cocaine intoxication that “facilitated a finding of cardiac death without a verifiable coronary stenosis,” they noted.

Postmortem 3-tesla MRI revealed chronic, subacute, and myocardial infarction, the authors concluded, and in cases of peracute infarction, MRI pinpoints the possible source of sudden cardiac death, demonstrating affected myocardial areas at autopsy, Jackowski and colleagues wrote.

More precision in defining cardiac death

The study is the first to amass a large number of cases presenting with hypointense T2-weighted lesions that are well-correlated to coronary events; among the 42 cases, there were 53 hypointense T2-weighted lesions that remained invisible at macroscopic dissection, the authors wrote.

“Knowing about the postmortem MR finding allowed for a targeted histological examination that showed early ischemic alterations in 62.3% of lesions,” they wrote. “Based on the present study, it is … expected that ischemic alterations would have not been detected in a routine histological examination without having the MR finding in advance.”

At MRI, no histological alteration could be seen within the affected myocardium in 37.7% of the cases, the authors cautioned. On the other hand, a comparison of hypointensity in MRI to coronary status at autopsy showed findings that were able to explain an ischemic situation within the myocardium in 84.9% of the cases, demonstrating solid value for the postmortem imaging technique. In daily practice, this suggests that MRI could explain the majority of unsatisfactory autopsy cases thought to be sudden cardiac death but without verifiable myocardial changes.

Among the study limitations cited by the authors, the design did not permit the use of a control group, and the researchers were not blinded to the results, they stated, adding that the gold standard, autopsy, has several known limitations that hamper comparison with imaging.

Postmortem cardiac imaging comes with the disadvantage of no late enhancement. But it may be more than compensated for by the lack of cardiac motion or breathing artifacts.

Before this study, “we have seen hearts that presented with older or no ischemic lesions and may have three-vessel disease, but no fresh lesion that could explain why the heart stopped working exactly at that time,” Jackowski told AuntMinnie.com. “We then speak about sudden death, meaning that an arrhythmic event might have caused the death. However, what causes the arrhythmia often remains unclear. With postmortem MRI, we do see myocardial areas that the arrhythmia possibly originates from, areas that remain hidden for the human eye at autopsy. In forensics, the cases can be solved better and more convincingly.”

Related Reading

Advances in forensic imaging bring new opportunities for radiology, March 10, 2013

Elsevier launches forensic radiology journal, February 11, 2013

New society represents forensic radiology, November 29, 2011

High-field MRI appropriate for fetal autopsy, August 18, 2009
Copyright © 2013 AuntMinnie.com



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Dilated Cardiomyopathy: Decisions on implantable cardioverter-defibrillators (ICDs) using left ventricular ejection fraction (LVEF) and Midwall Fibrosis: Decisions on Replacement using late gadolinium enhancement cardiovascular MR (LGE-CMR)

Reporter: Aviva Lev-Ari, PhD, RN

2 imaging studies offer intrigue but clinical gain remains in doubt

By Candace Stuart

Mar 06, 2013

Two separate studies edged delayed-enhancement cardiovascular MRI toward the clinical equivalent of home plate, but neither scored a run. The studies and an accompanying editorial were published March 6 in the Journal of the American Medical Association.

Ankur Gulati, MD, of Royal Brompton Hospital in London, and colleagues assessed the prognostic value of midwall fibrosis with late gadolinium enhancement cardiovascular MR (LGE-CMR) to predict adverse outcomes for patients with dilated cardiomyopathy. This condition may lead to progressive heart failure and sudden cardiac death (SCD); consequently, risk stratification beyond assessments based on left ventricular ejection fraction (LVEF) may help physicians tailor management plans, including selecting patients for implantable cardioverter-defibrillators (ICDs).

“Most patients who experience SCD do not have severely reduced LVEF, and many patients with significant impairment of LVEF may still be at low risk for SCD,” they wrote. About one-third of these patients have a characteristic midwall pattern of replacement fibrosis detected by LGE-CMR, which the authors suggested might be a predictor of mortality and SCD.

To test that hypothesis, they designed a prospective longitudinal study that enrolled 472 consecutive patients with dilated cardiomyopathy who were referred to their hospital between 2000 and 2008. The patients underwent LGE-CMR to evaluate the presence and extent of midwall fibrosis, with follow-up through December 2011. The primary endpoint was all-cause mortality and the secondary endpoints were cardiovascular mortality or heart transplantation, the composite of SCD or aborted SCD and the composite of heart failure, heart failure hospitalization and heart transplant.

Two independent readers who were blinded to clinical data assessed the presence of midwall fibrosis and an experienced operator quantified the extent of fibrosis. They verified deaths through national resources, death certificates and communications with physicians and families.

Patients had a mean LVEF of 37 percent and were followed for a median duration of 5.3 years. Thirty percent had midwall fibrosis with a median extent of 2.5 percent. The mortality rate for patients with midwall fibrosis was 26.8 percent compared with 10.6 percent for patients without midwall fibrosis and the presence of midwall fibrosis was associated with a higher risk of cardiovascular mortality or transplantation. Patients with midwall fibrosis had higher rates of SCD or aborted SCD (29.6 percent vs. 7 percent) and higher rates of the heart failure composite (25.4 percent vs. 11.2 percent).

Adding midwall fibrosis to a risk model decreased the mortality risk for patients with an LVEF of 35 percent and no midwall fibrosis from 12.7 percent to 9.4 percent and increased mortality risk for patients with midwall fibrosis from 12.7 percent to 19.9 percent. Twenty-nine percent of patients were correctly reclassified with the addition of midwall fibrosis status, Gulati et al determined.

“The addition of midwall fibrosis to LVEF resulted in significant improvements in risk reclassification for both all-cause mortality and the arrhythmic composite,” they wrote. “Our findings suggest that detection and quantification of midwall fibrosis by LGE-CMR may represent useful markers for the risk stratification of death, ventricular arrhythmia and HF [heart failure] for patients with dilated cardiomyopathy.”

They added that the information provided by imaging could help in identifying patients at high risk who would benefit from ICD implantation.

In the second study, Dipan J. Shah, MD, of the Duke Cardiovascular Magnetic Resonance Center in Durham, N.C., and colleagues evaluated patients with regional myocardial wall thinning to assess if they have minimal or no scarring using LGE-CMR. They suggested that such regions might represent viable myocardium. They enrolled 1,055 patients with coronary artery disease who underwent LGE-CMR imaging at three centers between 2000 and 2008.

The study was divided into three parts: first, to determine the prevalence of regional thinning; second, to evaluate the prevalence of limited scar burden (less than 50 percent) in thinned myocardium; and third, to evaluate the relationship between scar burden and functional burden and tissue remodeling in patients who received coronary revascularization.

Nineteen percent of the patients had myocardial wall thinning with thinning of a substantial (a mean of 34 percent) portion of the left ventricle (LV). Of those with wall thinning, 18 percent had scarring of less than 50 percent.

Seventy-two percent of patients underwent revascularization. Shah et al reported inverse relationships between the extent of scarring and contractile improvement after revascularization as well as myocardial remodeling, with only those patients with limited scar burden showing improvement. Based on those findings, they suggested that myocardial thinning may be reversible.

“[W]e have shown that the myocardial wall may thin and revert back to full thickness as long as limited scarring is present,” they wrote. “These results indicate that the end stage of remodeling is better determined by tissue composition (i.e., scarring) rather than any set level of morphological changes to the LV cavity or LV wall.”

In an accompanying editorial, Deepak K. Gupta, MD, Raymond Y. Kwong, MD, MPH, and Marc A. Pfeffer, MD, PhD, all of Brigham and Women’s Hospital in Boston, pointed to limitations in both studies. As a single center study using low-risk patients, Gulati et al’s findings may not apply to those patients who would most benefit from risk stratification, they wrote, and the study by Shah et al was subject to referral and selection bias.

“Collectively, these and other studies demonstrate that CMR with LGE imaging adds to the practitioner’s armamentarium for assessment of cardiac structure and function and augments diagnostic and prognostic capabilities,” the editorial writers offered.

But determining which patients to evaluate remained a challenge. “At this point, for the practicing physician, the incremental information gained from CMR with LGE imaging from these two studies, albeit novel and supportive, is not yet sufficient to alter clinical practice guidelines,” they concluded.



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A Word of Caution especially to Cardiacs’

Zithromax (azithromycin), is not only a more expensive antibiotic than other antibiotics but also seems to be an expensive one at Heart. Doctors should weigh other options for people already prone to heart problems, the researchers and other experts suggested. It is a popular antibiotic because it often can be taken for a fewer days compared to other antibiotics, for example: about 10 days for amoxicillin and other antibiotics and five-day course will suffice in case of Zithromax.


Azithromycin (Photo credit: Wikipedia)

It is widely used for bronchitis, sinus infections and pneumonia, and other common infections but seems to increase chances for sudden deadly heart problems. A rare but surprising risk found in a 14-year study. Also, antibiotics in the same class as Zithromax have been linked with sudden cardiac death. In the current study, patients those on Zithromax were about as healthy as those on other antibiotics, making it unlikely that an underlying condition might explain the increased death risk, researchers said.

Researchers analysis at Vanderbilt University indicates that there were 29 heart-related deaths among those who took Zithromax during five days of treatment. Their risk of death while taking the drug was more than double that of patients on another antibiotic, amoxicillin, or those who took none.

To compare risks, the researchers calculated that the number of deaths per 1 million courses of antibiotics would be about 85 among Zithromax patients versus 32 among amoxicillin patients and 30 among those on no antibiotics. The highest risks were in Zithromax patients with existing heart problems. Patients in each group started out with comparable risks for heart trouble, the researchers said. The results suggest there would be 47 extra heart-related deaths per 1 million courses of treatment with Zithromax. The risk of cardiovascular death was significantly greater with azithromycin than with ciprofloxacin but did not differ significantly from that with levofloxacin.

Dr. Harlan Krumholz, a Yale University health outcomes specialist who was not involved in the study said that “People need to recognize that the overall risk is low,”. More research is needed to confirm the findings, but still, he said patients with heart disease “should probably be steered away” from Zithromax for now.

At the same time, Dr. Bruce Psaty, a professor of medicine at the University of Washington, of opinion that doctors and patients need to know about the potential risks. He said the results also raise concerns about long-term use of Zithromax, which other research suggests could benefit people with severe lung disease. Additional research is needed to determine if that kind of use could be dangerous, he said.

The study appears in the New England Journal of Medicine. The National Heart, Lung and Blood Institute helped pay for the research. Wayne Ray, a Vanderbilt professor of medicine, studied the drug’s risks because of evidence linking it with potential heart rhythm problems.

Pfizer is committed to patients safety and issued a statement saying it would thoroughly review the study and “Patient safety is of the utmost importance to Pfizer and we continuously monitor the safety and efficacy of our products to ensure that the benefits and risks are accurately described,” the company said.


Additional info on Zithromax

Reported by Dr. Venkat Karra, Ph.D

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