Dear Editor

La Vecchia et al. [1] considered increased cardiac troponin on admission to be the strongest independent predictor of mortality in acute pulmonary embolism. They attributed the increased troponin to right ventricular involvement, because they excluded patients with known or prior coronary artery disease in their study. The criteria they used for exclusion were documented angina, previous myocardial infarction, coronary angioplasty or bypass surgery.

But they have not excluded coronary embolism which can occur in patients without prior, known coronary artery disease. As a matter of fact, paradoxical coronary embolism has been reported in patients with increased pulmonary artery pressure, e.g. pulmonary embolism [2,3] or increased right atrial pressure, e.g. Valsalva maneuver or cough.[2-4] It also accounts for ST segment elevation in right precordial leads on ECG in patients with acute pulmonary embolism.[5,6] Paradoxical coronary embolism may contribute to the increased mortality in patients with acute pulmonary embolism.[7,8] Finally, the diagnosis of paradoxical embolism in acute pulmonary embolism carries an important therapeutic implication, because patent foramen ovale, the commonest cause of paradoxical embolism, can now be closed nonsurgically.[9]

References

1. La Vecchia L, Ottani F, Favero L, Spadaro GL, Rubboli A, Boanno C, Mezzena G, Fontanelli A, Jaffe AS: Increased cardiac troponin I on admission predicts in-hospital mortality in acute pulmonary embolism. Heart 2004;90:633-637.

2. Cheng TO: Paradoxical embolism. A diagnostic challenge and its detection during life. Circulation 1976;53:565-568.

3. Cheng, TO: Paradoxic embolism. Am Heart J 1996;131:1238.

4. Cheng TO: Paradoxical embolism: diagnosis and management. J Emerg Med 2001;20:416-417.

5. Cheng TO: Right-sided chest-lead abnormalities on EKG in acute pulmonary embolism. J Nat Med Assoc 2003;95:862.

6. Cheng TO: Brugada syndrome vs pulmonary embolism vs paradoxical embolism. What are we to believe? Int J Cardiol 2004;94:119.

7. Kasper W, Konstantinides S, Geibel A, Olschewski M, Heinrich F, Grosser KD, Rauber K, Iversen S, Redecker M, Kienast J: Management strategies and determinants of outcome in acute major pulmonary embolism: results of a multicenter registry. J Am Coll Cardiol 1997;30:1165-1171.

8. Konstantinides S, Geibel A, Kasper W, Olschewski M, Blümel L, Just H: Patent foramen ovale is an important predictor of adverse outcome in patients with major pulmonary embolism. Circulation 1998;97:1946-1951.

9. Cheng TO: Percutaneous closure of patent foramen ovale is the procedure of choice for paradoxical embolism. Circulation 2003;108:e126.

Dear Editor,

While the role of internal defibrillator, as a life-saving device, is established in Brugada syndrome, drugs like betablockers may precipitate a Brugada phenotype and are ineffective in this syndrome, therefore not recommended [1].

Reference

1. Charles Anzelevitch, Pedro Brugada, Martin Borggreffe. Brugada syndrome. Report of the second consensus conference. Circulation. 2005;111:000-000.

Dear Editor,

Why should lipid lowering drugs be associated with an increased risk of developing peripheral neuropathies [1,2]? For the same reason that rapid glycaemic control might be [3]? That would imply that fatty acids can be used as a substrate for oxidative phosphorylation in the brain just as it is peripherally and the current view is that it cannot. The brain can use glucose and in some circumstances ketone bodies but it is claimed not fatty acids.

What almost every in vitro biochemical experiment has done has been to buffer pH and gas with 95% O2 and 5% CO2. [That is a highly abnormal state]. What is more the liver has been excluded and hence the opportunity for recycling anaerobic metabolites and maintaining ATP resynthesis by anaerobic glycolysis. [The same applies to almost every in vitro experiment that has been performed on the heart]. In any event the brain [and even the heart] contains large amounts of lipid [4] a significant portion of which must exist in mobile pools.

Might a lipid shift increase the efficiency of ATP resynthesis during reductive stress in the brain just as it has been proposed to do peripherally? Being highly diffusable ketone bodies might operate a particularly effective shuttle analogous to that proposed in the lactate shuttle hypothesis. If so might lipid lowering drugs compromise this in patients exposed to some degree of reductive stress and who might have become dependent upon this source of nutrient for efficient neurological energy metabolism as proposed might be the case in diabetics?

References

1. Corrao G, Zambon A, Bertu L, Botteri E, Leoni O, Contiero P. Lipid lowering drugs prescription and the risk of peripheral neuropathy: an exploratory case-control study using automated databases. J Epidemiol Community Health. 2004 Dec;58(12):1047-51.

2. G Corrao, A Zambon, L Bertù, E Botteri, O Leoni, and P Contiero Lipid lowering drugs prescription and the risk of peripheral neuropathy: an exploratory case-control study using automated databases Heart 2005; 91: 560.

3. Grounds for abandoning "diabetes" as a diagnosis? Richard G Fiddian-Green (9 March 2005) eLetter re: M K S Leow and J Wyckoff Under-recognised paradox of neuropathy from rapid glycaemic control Postgrad Med J 2005; 81: 103-107.

4. Isabelle Carriéa,b, Michel Clémenta, Dominique de Javelb, Henriette Francèsa, and Jean-Marie Bourrea Specific phospholipid fatty acid composition of brain regions in mice: effects of n;–3 polyunsaturated fatty acid deficiency and phospholipid supplementation Journal of Lipid Research, Vol. 41, 465-472, March 2000.

Dear Editor,

The recent review of stress echocardiography in Heart is a good overview of a technique which has clearly come of age [1]. However it really is time that the echo community stopped being so defensive about the alternative technique of myocardial perfusion scintigraphy (MPS).

In November 2003 the National Institute for Clinical Excellence (NICE) published the positive results of its Technology Appraisal 73, entitled “Myocardial perfusion scintigraphy for the diagnosis and management of angina and myocardial infarction” [2]. The value of myocardial perfusion scintigraphy (MPS) as a mature diagnostic and prognostic investigation was recognised, and it was estimated that an approximately four-fold increase in MPS activity in the UK might be appropriate. The Appraisal has aroused much controversy, particularly from proponents of stress echocardiography, who feel that NICE should have considered the full range of non-invasive tests available for patients with known or suspected coronary disease. This grievance has spilled over into the review cited above, and the authors have erred in making ill-informed negative comments about MPS.

The stock objections to MPS raised by the authors are that “its widespread use is limited by cost, radiation, and relative lack of availability” [1]. It is time that these myths were dispelled, beginning with the cost argument. A small-field-of-view dedicated cardiac gamma camera now costs the same as a decent echo machine, and both require one member of staff for scanning and a similar sized room. The facilities required for stress in terms of space, hardware, and staff (usually two in the room) are independent of the imaging modality being used. The cost of consumables is roughly the same for both imaging modalities, and is dominated by the price of the radiopharmaceutical (MPS) or echo contrast agent (stress echo). One important advantage of MPS is that, compared with other modalities, the imaging side of MPS is fixed and automated so that the requirement for “hands-on” consultant time (an expensive resource in the NHS) is limited to reporting. Ultimately, any difference in the cost per patient between modalities is largely a function of patient throughput, which can be extremely efficient using MPS with a dedicated cardiac gamma camera (more than 2000 patients per year).

The radiation argument is specious. The effective dose equivalent from a MPS study performed using a modern technetium-99m-based tracer is 10mSv, which is similar to that from a coronary angiogram or CT scan [3]. In a healthy 40 year old male, after a 10 year latency period, this confers an increased risk of developing cancer of 1 in 3000, compared with a background lifetime risk of 1 in 6. Radiation exposure is (rightly in our opinion) not a consideration when deciding, for example, whether a patient should have an abdominal CT scan instead of an abdominal ultrasound, or prior to coronary angiography, and so the focus on nuclear medicine procedures in this regard is difficult to understand.

The argument that MPS in inherently more difficult to set up and therefore less available than other imaging modalities is demonstrably false internationally. In a recent European survey of 3779 patients presenting to a cardiologist with angina, a stress-based imaging test was performed in 18% of cases [4]. This test was MPS in 95% of patients in northern Europe (including the UK), 91% in the Mediterranean, 84% in western Europe, and 66% in central Europe: clearly our European colleagues are unaware that MPS is more difficult to set up than its alternatives. The only real difficulty, particularly in the UK, is the tight regulatory framework which governs nuclear medicine procedures. However, the majority of reasonably sized district general hospitals already have a nuclear medicine department, and so the framework is almost always already in place.

The real reason that MPS has been slow to be adopted in the UK is “political”. MPS, in contrast to other cardiac imaging techniques, is usually performed by radiologists and nuclear physicians rather than cardiologists. This makes alternative cardiologist-led techniques such as stress echocardiography more attractive when a functional imaging test is required. The answer to this is not to disparage MPS itself, but to motivate cardiologists to become more involved. This has occurred in the USA, where more than 20,000 MPS studies per million population per year are currently performed (compared with 5000 across Europe and just over 1000 in the UK).

In reality, The UK is so far behind the rest of the developed World in terms of noninvasive imaging for coronary disease that squabbles between the proponents of the various imaging modalities are an unhelpful distraction. The clinical information provided by all of the stress-based imaging tests, when performed by appropriately skilled staff, is more-or-less equivalent. It matters little how many of the 4000 patients pmp per year identified by NICE undergo stress echocardiography rather than MPS: if the wider cardiology community accepts that functional imaging is a valuable exercise, there will be more than enough work for all of us.

References

[1] Senior R, Monaghan M, Becher H, Mayet J, Nihoyannopoulos P. Stress echocardiography for the diagnosis and risk stratification of patients with supected or known coronary artery disease: a critical appraisal. Heart 2005; 91: 427-436.

[2] http://www.nice.org.uk/TA073guidance

[3] Picano E. Informed consent and communication of risk from radiological and nuclear medicine examinations: how to escape from a communication inferno. BMJ 329: 849-51.

[4] Daly CA, Clemens F, Lopez Sendon JL, Tavazzi L, Boersma E, Danchin N, et al. The clinical characteristics and investigations planned in patients with stable angina presenting to cardiologists in Europe: from the Euro Heart Survey of Stable Angina. Eur Heart J 2005 (E-published ahead of print).