Letters · Correspondance

CMAJ 1999;161:941-6

• CABG in Canada W.A. Ghali, et al
• Does treating hypertension protect against dementia? A.M. Clarfield; response: C.J.S. Patterson
• Debating the patient's "right to know" R. Robson; response: E.H.W. Kluge; C.D. Naylor
• Fruitful discussions about drug interactions J.D. Spence
• Concerns about size of MD workforce, medicine's future dominate CMA annual meeting [Correction]

In 2 recent CMAJ articles [full article]¹, [full article]² we reported a favourable national trend of decreasing risk-adjusted rates of death after coronary artery bypass graft (CABG) surgery over 4 fiscal years — 1992/93 through 1995/96. The 17% relative decline in adjusted death rates over this period was judged to be comparable to the declines seen over similar periods in various regions of the United States.^3­6 We now briefly report results of more recent analyses that include data from 2 additional fiscal years, 1996/97 and 1997/98.

The updated results (Table 1) were generated using hospital discharge data from the Canadian Institute for Health Information. This data source provides information on CABG surgery cases from all provinces except Quebec. We performed risk adjustment analyses to control for differences in average severity of illness across years using the methods described in our original articles.^1,2

These data demonstrate a steady increase in the number of CABG procedures performed each year and continuing improvement in both observed and adjusted death rates after CABG surgery, despite a concomitant increase in expected death rates. The latter suggests that, on average, patients selected for CABG surgery are becoming sicker and their cases more complex, and yet they are more likely to experience favourable short-term outcomes after surgery. The 29.5% relative decline in risk-adjusted death rates seen over 6 years is unlikely to be the result of "upcoding" of severity of illness, because the coding of hospital discharge data is not done by the clinicians who care for the patients and because the observed death rates (which are not subject to coding biases) also dropped considerably.

Although the reasons for the improved outcomes are not clear from our analyses, we would nonetheless propose that collective congratulations ought to be extended to the community of cardiologists, intensivists, anesthetists and cardiac surgeons who care for these patients.

William A. Ghali, MD, MPH
Hude Quan, MD, PhD
Rollin Brant, PhD
Departments of Medicine and Community Health Sciences
University of Calgary
Calgary, Alta.

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1. Ghali WA, Quan H, Brant R. Coronary artery bypass grafting in Canada: national and provincial mortality trends, 1992-1995. CMAJ 1998;159(1):25-31.
2. Ghali WA, Quan H, Brant R. Coronary artery bypass grafting in Canada: hospital mortality rates, 1992­1995. CMAJ 1998;159(8):926-30.
3. Peterson ED, Jollis JG, Bebchuk JD, Delong ER, Muhlbaier LH, Mark DB, et al. Changes in mortality after myocardial revascularization in the elderly. Ann Intern Med 1994;121:919-27.
4. Hannan EL, Kilburn H Jr, Racz M, Shields E, Chassin MR. Improving the outcomes of coronary artery bypass surgery in New York State. JAMA 1994;271:761-6.
5. O'Connor GT, Plume SK, Olmstead EM, Morton JR, Maloney CT, Nugent WC, et al, for the Northern New England Cardiovascular Disease Study Group. A regional intervention to improve the hospital mortality associated with coronary artery bypass graft surgery. JAMA 1996;275:841-6.
6. Ghali WA, Ash AS, Hall RE, Moskowitz MA. Statewide quality improvement initiatives and mortality after cardiac surgery. JAMA 1997;277:379-82.

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I enjoyed reading the guidelines from the Canadian Consensus Conference on Dementia [full article]¹ as well as the excellent physician's guide to using the recommendations [full article].² Having taken part in the conference, I can attest to the fact that the material published in your pages accurately reflects the deliberations at the meeting.

Despite my overall support for the guidelines, I must disagree with the statement that "the treatment of hypertension reduces the incidence of not only vascular dementia but also Alzheimer's disease" in scenario 4 of the physician's guide.² The authors cite an article by Forette and colleagues,³ who make claims that are far too optimistic given the evidence they present. Forette and colleagues describe the Systolic Hypertension in Europe (Syst­Eur) trial, a secondary goal of which was to reduce the incidence of vascular dementia by the treatment of isolated systolic hypertension. Only 2 cases of vascular dementia occurred, far fewer than had been originally predicted. It was also found that treatment of hypertension apparently reduced the incidence of Alzheimer's disease and mixed and vascular dementias by 50%. Although this finding is interesting, it should be pointed out that the confidence interval around the estimate of a 50% reduction included 0. Thus, the data are also just as compatible with no treatment effect. Forette and colleagues' results constituted a post-hoc analysis, suggesting the possibility of false-positive results.

Of interest as well is the fact that the only comparable study (the Systolic Hypertension in the Elderly Program [SHEP]), while using different drugs than those used in the Syst­Eur trial, found no protection against dementia with control of systolic hypertension.⁴ A colleague and I have pointed out our objections to Forette and colleagues' overly optimistic claims in more detail elsewhere.⁵

Further trials are needed to determine whether treatment of hypertension will in fact reduce the incidence of vascular dementia and Alzheimer's disease, especially in the frail elderly suffering from comorbidity. In the meantime, we must continue to approach the decision to treat systolic hypertension in the very elderly with great care, lest we do more harm than good in treating them.

A. Mark Clarfield, MD
Sara Herzog Hospital
Jerusalem, Israel

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1. Patterson CJS, Gauthier S, Bergman H, Cohen CA, Feightner JW, Feldman H, Hogan DB. Management of dementing disorders: conclusions from the Canadian Consensus Conference on Dementia. CMAJ 1999;160(12 Suppl):S1-15.
2. Patterson CJS, Gauthier S, Bergman H, Cohen CA, Feightner JW, Feldman H, Hogan DB. Canadian Consensus Conference on Dementia: a physician's guide to using the recommendations. CMAJ 1999;160(12):1738-42.
3. Forette F, Seux ML, Staessen JA, Thijs L, Birkenhäger WH, Babarskiene MR, et al. Prevention of dementia in randomised double-blind placebo-controlled Systolic Hypertension in Europe (Syst­Eur) trial [see comment]. Lancet 1998;352:1347-51. Comment in: ACP J Club 1999;130:57.
4. SHEP Cooperative Research Group. Prevention of stroke by antihypertensive drug and treatment in older persons with isolated systolic hypertension. Final results of the Systolic Hypertension in the Elderly Progam (SHEP). JAMA 991;265:3255-64.
5. Clarfield AM, Paltiel O. Prevention of dementia in randomised double-blind placebo-controlled Systolic Hypertension in Europe (Syst­Eur) trial [comment]. ACP J Club 1999;130:57. Comment on: Lancet 1998;332:1347-51.

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We acknowledge that our interpretation of the Syst­Eur trial was overly optimistic. Many criticisms have been levelled at this trial as reported by Forette and colleagues.^1­3 In the intention-to-treat analysis the incidence of all dementia was apparently reduced by 50%. Although this reduction, from 7.7 to 3.8 cases per 1000 patient-years, was statistically significant (p = 0.05), the 95% confidence interval (CI) was 0%­76%. In the per-protocol analysis, reduction was 60% (p = 0.03) and the 95% CI was 2%­83%.⁴ It has been pointed out that there appeared to be a large number of subjects not completing the protocol and that assignment of as few as 2 of these subjects could change the conclusions.² However, Forette and colleagues reported that when subjects who could not be traced before publication were subsequently included in the analysis, the original conclusions were validated.⁵

The intention of Forette and colleagues' study was to determine whether antihypertensive treatment would reduce the incidence of vascular dementia.⁴ The finding of only 2 incident cases of vascular dementia among 32 cases of all dementia is not surprising. Although vascular dementia is considered to be much less common now than in the past, its distinction from Alzheimer's disease is less clear than once thought. Not only do they share common risk factors,⁶ but there is mounting evidence that the occurrence of strokes in people with Alzheimer's neuropathological changes may precipitate or exaggerate the clinical manifestations of dementia.⁷

These observations provide a plausible rationale for the findings of Forette and colleagues. However, the SHEP study failed to demonstrate that antihypertensive treatment reduced the incidence of dementia.⁸ These apparently conflicting results might be explained by differences in the 2 study populations; for example, the mean pretreatment diastolic blood pressure was 10 mm Hg lower in the SHEP study than in the Syst­Eur trial. It has been suggested that the use of a calcium-channel blocker in the Syst­Eur study could explain the apparent difference in findings.^4,9 However, data from the Canadian Study of Health & Aging indicate that people with hypertension who were taking calcium-channel blockers were more likely to experience a decline in cognitive performance than those taking other antihypertensive medications [full article].¹⁰

We thank Mark Clarfield for his observations and hope that this debate will be settled by a definitive trial using all causes of dementia as an end point. Indeed, such a study is already under-way, the Study on Cognition & Prognosis in the Elderly (SCOPE).¹¹ In the meantime we hope that systolic hypertension will be appropriately recognized and treated in older people, as this will reduce the incidence of stroke. Whether such treatment will also decrease the incidence of dementia remains to be seen.

Christopher J.S. Patterson, MD
McMaster University
Hamilton, Ont.
David B. Hogan, MD
University of Calgary
Calgary, Alta.

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1. Clarfield AM, Paltiel O. Prevention of dementia in randomised double-blind placebo-controlled Systolic Hypertension in Europe (Syst­Eur) trial [comment]. ACP J Club 1999;130:57. Comment on: Lancet 1998;332:1347-51.
2. Pahor M, Somes GW, Franse LV, Shorr RI, Applegate WB. Prevention of dementia: Syst­Eur trial [letter]. Lancet 1999;353:235.
3. Zuccalà G, Pedone C, Cocchi A, Bernabei R, Carbonin P. Prevention of dementia: Syst­Eur trial [letter]. Lancet 1999;353:235-6.
4. Forette F, Seux ML, Staessen JA, Thijs L, Birkenhäger WH, Babarskiene MR, et al. Prevention of dementia in randomised double-blind placebo-controlled Systolic Hypertension in Europe (Syst­Eur) trial [see comment]. Lancet 1998;352:1347-51. Comment in: ACP J Club 1999;130:57.
5. Forette F, Staessen JA, Thijs L, Birkenhager WH. Author's reply [letter]. Lancet 1999;
   353:236-7.
6. Skoog I. The relationship between blood pressure and dementia: a review. Biomed Pharmacother 1997;51:367-75.
7. Snowdon DA, Greiner LH, Mortimer JA, Riley KP, Greiner PA, Markesbury WR. Brain infarction and the clinical expression of Alzheimer's disease: the NUN study. JAMA 1997;277:813-7.
8. SHEP Cooperative Research Group. Prevention of stroke by antihypertensive drug and treatment in older persons with isolated systolic hypertension. Final results of the Systolic Hypertension in the Elderly Program (SHEP). JAMA 1991;265:3255-64.
9. Kazuomi K, Pickering TG. Calcium antagonist and prevention of dementia in elderly people [letter]. Lancet 1999;353:1184.
10. Maxwell CJ, Hogan DB, Ebly EM. Calcium-channel blockers and cognitive function in elderly people: results from the Canadian Study of Health and Aging. CMAJ 1999;161:501-6.
11. Hansson LH, Skoog I, Banki CM, Baro F, Bretcler M, et al (for the SCOPE Investigators). Study on Cognition and Prognosis in the Elderly (SCOPE). Blood Press. In press.

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I write further to the contributions by Eike-Henner W. Kluge [full article]¹ and C. David Naylor [full article]² on whether physicians' practice profiles should be made available to the public.

Kluge's proposal is much like Swiss cheese — tantalizing but full of holes. Even if we accept Kluge's expansion of the concept of informed consent — and some recent lower court decisions suggest he is on the right track — there is no evidence in his article that the information he proposes to provide to patients and (or) health care consumers is relevant or helpful in selecting a competent physician. Naylor does a good job of pointing out the practical problems associated with Kluge's suggestion and of proposing how we might find solutions.

The question that needs to be answered is whether there is any connection between a physician's involvement in a legal action or a disciplinary proceeding and the competence of that physician (not to mention the ability to provide quality care in a compassionate manner acceptable to patients). Although licensing bodies can begin to look at this question, there is only one source that provides the link with legal actions — the Canadian Medical Protective Association (CMPA).

The CMPA's annual reports indicate that it has a database of almost 20 000 legal actions involving Canadian physicians. Several hundred disciplinary matters and several thousand matters regarding licensing body complaints are also available for analysis. We must begin to learn from this gold mine of bad outcomes. To date, the efforts of the CMPA's own Education and Research Department, although interesting, have not begun to address even remotely the questions raised by Kluge and Naylor.

Any such analysis must be done in a fashion that meticulously respects confidentiality. It is hard to imagine that conditions could not be put in place that would overcome the CMPA's reticence about allowing outside physicians access to data. Indeed, it is very hard to imagine that a research scientist of Naylor's reputation should not be allowed to examine the potential relationship between a physician's involvement in a legal action or disciplinary matter or both, and the competence of that physician through analysis of the CMPA database.

For the CMPA to allow such a scientific and confidential examination of the database would be to provide some of the basic building blocks that will ensure the provision of quality care to patients in Canada. Even as it continues to provide physicians with legal defence assistance, the CMPA can also play an important role in helping to develop a better understanding of the issues raised by Kluge and Naylor.

Where is evidence-based medicolegal investigation when we really need it?

Robert Robson, MD CM
Independent Health Care Liability and Risk Management Consultant
Nepean, Ont.

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1. Kluge EHW. Informed consent in a different key: physicians' practice profiles and the patient's right to know. CMAJ 1999;160(9):1321-2.
2. Naylor CD. Reporting medical mistakes and misconduct. CMAJ 1999;160(9):1323-4.

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I thank Robert Robson for likening my proposal to Swiss cheese, which is a classic that has stood the test of time, the holes notwithstanding. If my proposal attains similar status, I shall be well pleased.

Jokes aside, his letter raises 2 interesting and important points: that it is up to the medical profession and "research scientists" to decide what information about physicians is appropriate or useful for patients to know before they select a doctor, and that the CMPA is the appropriate agency to provide such information.

Regarding the former, it strikes me as odd that Robson, a risk-management consultant, should have missed the point of my ethical analysis and the significance of the lesson provided in Reibl v. Hughes¹ and McInerney v. MacDonald.² In these cases the courts stated very clearly that it is not up to the medical profession to decide what should be revealed and what may be withheld from a patient. Arguing the very ethics of informed consent that I sketched in my article, the court stated that the standard of disclosure should be what the objective, reasonable person in the patient's position would want to know. Therefore, both the ethics and case law make it very clear that it is not up to the medical profession (or research scientists) to decide what should and what should not be revealed. It also bears emphasizing that these decisions were not "some recent lower court decisions" but rulings by the Supreme Court of Canada.

As for the second point, I think the CMPA would be the last agency one would turn to for the information Robson mentions. The CMPA's mandate is to provide legal assistance to physicians, so its perspective is litigious and physician oriented. How would this organization address the ethics of patients' demands for information on physicians? Further, the CMPA's mandate is not to do longitudinal follow-up studies of the practice patterns of physicians who have been subjected to legal or disciplinary action. Consequently, the CMPA database could not possibly yield the information that Robson suggests is relevant. Databases of the licensing authorities could do this, a fact I did not mention in my article because of space limitations.

In the end, I believe that the court findings in Reibl v. Hughes and McInerney v. MacDonald — as well as in Malette v. Shulman³ — speak for themselves.

Eike-Henner W. Kluge, PhD
University of Victoria
Victoria, BC

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1. Reibl v. Hughes [1980], 2 SCR 880.
2. McInerney v. MacDonald [1992] 2 SCR 138.
3. Malette v. Shulman [1990], 67 DLR (4th) 321.

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I will address one issue that, from media accounts, has galvanized public interest in seeking more publicity about college disciplinary proceedings: venue-shopping by physicians who have lost their licences in one province and successfully seek licensure elsewhere. I do not know how often this occurs, but the solution is tougher and more consistent self-regulation. This includes cooperation among the colleges to keep sexually abusive, chronically impaired or incompetent physicians out of practice in every province unless there is unequivocal evidence that it is safe for them to resume clinical work — with or without ongoing conditions and supervision.

I understand that the Federation of Medical Licensing Authorities of Canada has initiated more systematic sharing of information on discipline and assessment proceedings, and it is also testing a system of unique national identifiers for all licensed physicians [full article].¹

As Robson argues, available research suggests that successful malpractice suits are neither specific nor sensitive measures of clinical competence. Disciplinary actions appear more specific but are hopelessly insensitive to most of the systematic quality problems in modern medical care. Although I accordingly question whether individual patients will truly benefit from better access to this information, informed consent is not the only rationale for Kluge's proposal. In an essential-service sector where the state has ceded substantial self-regulatory privileges to providers, the balance must inevitably be weighted in favour of transparency — the public's "right to know." With due attention to practicalities and potential pitfalls, Kluge's proposal merits serious consideration on the latter grounds alone.

C. David Naylor, MD
University of Toronto
Toronto, Ont.

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1. Wharry S. Every MD will soon have unique "cradle-to-grave" identifying number. CMAJ 1999;160(6):896.

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I was struck by the similarity of a recent CMAJ editor's preface on drug interactions [full article]¹ to a piece I wrote a couple of years ago.² To date the drug interactions with grapefruit appear to include inhibition of gut wall cytochrome P450 3A4 by naringin and dihydroxybergamottin,³ as well as an interaction with P-glycoprotein.⁴ In the case of drug­drug interactions, there are mechanisms for warning physicians, pharmacists and patients. However, in the case of grapefruit, special efforts are required: grocers seldom take a drug history when dispensing grapefruit.

In the Australian state of Victoria, it has been required for some time that pharmacists provide warnings when dispensing some drugs with known grapefruit interactions⁵; however, not all drugs have been tested for the interaction.

A simple rule of thumb for anticipating grapefruit interaction with drugs is that if erythromycin is a problem, then grapefruit is a problem.

J. David Spence, MD
Siebens­Drake/Robarts Research Institute
London, Ont.

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1. Drug interaction: Who warns the patient? [editor's preface]. CMAJ 1999;161(2):117.
2. Spence JD. Drug interactions with grapefruit juice: Whose responsibility is it to warn the public? Clin Pharmacol Ther 1997;61:395-400.
3. Bailey DG, Arnold JMO, Bend JR, Tran LT, Spence JD. Grapefruit juice ­ felodipine interaction: reproducibility and characterization with the extended release drug formulation. Br J Clin Pharmacol 1995;40(2):135-40.
4. Soldner A, Christians U, Susanto M, Wacher VJ, Silverman JA, Benet LZ. Grapefruit juice activates P-glycoprotein-mediated drug transport. Pharm Res 1999;16:478-85.
5. Roller L. Drugs and grapefruit juice. Clin Pharmacol Ther 1998;63:87.

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A recent article stated incorrectly that Raheem Kherani of Edmonton is president of the Canadian Federation of Medical Students.¹ When the article was written, that post was held by Marc Zerey of McGill University and Kherani was the federation's western regional representative. We apologize for this error.

The online version is correct.

1. Sullivan P. Concerns about size of MD workforce, medicine's future dominate CMA annual meeting. CMAJ 1999;161(5):561-2.