Doctor's Review: Medicine on the Move

August 18, 2017

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Conference Proceedings: 2012 Scientific Sessions of the AHA

I ♥ LA

The American Heart Association (AHA) is arguably the most influential specialist physicians' association on the planet, yet its conference — November 3 to 7 in LA last year — doesn't always make a big splash in the press. Reading the newspapers, one might think cardiology is a fairly quiescent field right now. Nobody attending the LA conference would come away with that impression.

The meeting boasted a resuscitation science symposium, a cardiovascular nursing clinical symposium, an international forum highlighting 10 countries that lead the way in CVD research and a “Case Theater” where experts presented and discussed 30-minute recordings of their latest surgical techniques. The number of late-breaking abstracts allowed in — 27, no less — gives some idea of the sheer volume of research presented at LA's Convention Center.

Statins and diabetes

Any medical professional not living under a rock must have heard by now that statins are being linked to added risk of diabetes. This suspicion has generated plenty of research, which was pooled, analyzed and summarized in a special session at AHA 2012. The bottom line is that, yes, statins do increase diabetes risk, but only slightly, and this risk is heavily outweighed by cardiovascular benefits. Dr David Waters of San Francisco General Hospital put it succinctly, noting that statin therapy has been called a double-edged sword: “It is. But one edge is an awful lot sharper than the other.”

All five studies presented showed increased risk of diabetes in patients on statins, but the absolute risk increase was small, about two cases per 1000 patient-years. Risk was correlated to pre-treatment diabetes risk status and to statin dosage. There also appeared to be a synergistic effect from niacin, diuretics, beta-blockers and antidepressants. Indeed the flurry of research has revealed that statins aren't the only common drugs to increase diabetes risk. New analysis of data from the 2010 NAVIGATOR trial1 gave hazard ratios for developing diabetes with statins, diuretics, and beta-blockers of 1.30, 1.35 and 1.19 respectively, while calcium channel blockers were acquitted of the charge.

The larger story is well told by a high-quality Taiwanese study looking at prediabetic patients not taking antihyperglycemic drugs. Of those on statins, 8.5% developed diabetes and all-cause mortality was 1.4%. Of those not on statins, 7.1% developed diabetes, but all-cause mortality was dramatically higher at 2.4%.

Dr Barton Duell of Oregon Health & Science University, who led the AHA discussion, summed up: “Although it does appear that statins may increase the risk of diabetes in high-risk patients, this should not stop us from using these drugs, as this small risk is outweighed by the substantial reduction in cardiovascular events…. These really are excellent drugs, but new strategies are needed to help reduce the risk of diabetes in statin users, such as increased use of bile-acid sequestrants, reduced use of niacin, and better glucose monitoring."

The fields of diabetes and cardiology are slowly merging, as more and more patients appear with both conditions. Diabetes often alters the treatment equation for CVD and this was made clear by the FREEDOM study presented in LA.2 Mainstream cardiology is moving away from open surgery and towards angioplasty — with the AHA now even discussing same-day discharges after percutaneous coronary intervention (PCI) — but FREEDOM showed a clear survival benefit from CABG over PCI in patients who have diabetes and multivessel coronary artery disease, due to the added risk of stent occlusion that comes with diabetes.

Cold comfort

It's old news that cardiovascular deaths spike in the winter. And we know that cold temperature increases blood pressure and constricts vascular walls. We naturally assumed the two facts were connected. Not necessarily so, according to Dr Bryan Schwartz of the Good Samaritan Hospital, Los Angeles, who studied seasonal cardiac death rates within the US and found the same pattern in Texas and Arizona as in Pennsylvania and Massachusetts.3 "If it were only temperature, these curves would have reflected that, but the curves were exactly the same," he said.

"Each location in the wintertime had approximately an 18% increase over the average, and in each location in the summertime there was an approximate 10% to 12% decrease from the average yearly death rate,” explained Dr Schwartz. “We found this to be surprising. We thought that colder climates with a colder winter would have a greater increase in mortality in the wintertime... but that's not what we found."

That leaves plenty of plausible culprits other than cold weather for the winter spike, including reduced vitamin D, less exercise and more circulating respiratory infections. Indeed, the same researchers showed the AHA how, in Texas, respiratory infections are significantly correlated with ischemic heart disease deaths throughout the year.4

Back from the dead

One circumstance in which you want a cardiac patient to be cold is after resuscitation following an out-of-hospital cardiac arrest. These cases often have grim neurological outcomes, which are known to be ameliorated by cooling the patient with refrigerated intravenous saline. But the optimum body temperature remained unknown.

Dr Esteban López-de-Sá of La Paz University Hospital, Madrid, won fulsome praise for conducting a controlled study in the frantic circumstances of ongoing cardiac arrest.5 He was able to show that, among patients admitted with a shockable rhythm, cooling to 32oC for 24 hours left far more patients able to fend for themselves after recovery than cooling to 34oC. Eight of 18 patients in the 32oC group were living without severe dependence after six months compared to two of 18 in the 34oC group.

Resuscitation has been on the collective mind of the AHA recently, which is why they funded, with the National Institutes of Health, the Get With The Guidelines - Resuscitation quality improvement program, with its strong research component. We've all guffawed at the TV doctor shows where the dedicated clinician keeps trying CPR after everyone else has given up and finally brings back an apparently unharmed patient from the dead. This scenario may be less unlikely than it looks. The NIH-AHA program has found that patients at hospitals with the longest median duration of resuscitation efforts (25 minutes) had a 12 percent higher likelihood of being revived than patients at hospitals with the shortest median time of 16 minutes.6 Remarkably, those who survived after longer efforts appeared to have neurological function not much worse than patients who responded early. The AHA is still digesting this finding, which is likely to change guidelines and standard practice.

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