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The Expanding Scope of CoronaryAngioplasty

SEVEN years after its introduction,’ percutaneoustransluminal coronary angioplasty (PTCA) hasbecome the invasive treatment of first choice for asizeable minority of patients who would otherwise becandidates for coronary artery surgery. The advancesthat have made this possible are the development of softsteerable guidewires,2,3improved pressure toleranceand design of balloons,4,5 and the increasing skill ofoperators, who can now treat disease involving morethan one vessel. As a result of these advances, patientswith more severe symptoms are being treated byPTCA than was the case previously, and patients whowere formerly treated surgically are now beingconsidered for PTCA. Between a quarter and half ofthe patients who would have needed surgery in the pastare now suitable for PTCA.Success rates for dilatation of stenotic lesions

increase with the experience of the operator. Data froma PTCA registry involving 105 centres between 1979and 1981 showed a primary success rate of 55% forinvestigators with fewer than 150 cases rising to 77%after 150 procedures.6 Increasing success was not dueto case selection but to greater ability to cross thelesions with the catheter. More recent reports fromnine investigators during 1983 7 showed primary

1 Gruentzig AR. Transluminal dilation of coronary artery stenosis. Lancet 1978; i 2632. Simpson JB, Baim DS, Rebert EW, Harrison DC. A new catheter system for coronary

angioplasty Am J Cardiol 1982; 49: 1216-22.3. McAuley BJ, Oesterle S, Simpson JB. Advances in guidewire technology. Am J Cardiol

1984; 53: 94C-96C.4. Meier B, Gruentzig AR, King SB, et al. Higher balloon dilatation pressure in coronary

angioplasty. Am Heart J 1984, 17: 619-22.5 Meier B. Kissing balloon coronary angioplasty. Am J Cardiol 1984; 54: 918-20.6. Kelsey SF, Mullin SM, Detre KM, et al. Effect of investigator experience on

percutaneous transluminal coronary angioplasty Am J Cardiol 1984; 53: 56C-64C.7. Meier B, Gruentzig AR. Learning curve for percutaneous transluminal coronary

angioplasty, skill, technology or patient selection. Am J Cardiol 1984; 53:65C-66C

success rates of up to 94% (mean 87%) for the latest50 cases of these nine investigators. The majorcomplications ofPTCA are myocardial infarction (5%of cases) and death ( 1 °70). A further 7% have prolongedangina but no infarction.8 Emergency surgery is

necessary in about 5-7070 of cases.9 Myocardialinfarction usually occurs within 24 hours of dilatationand is caused by coronary occlusion or dissection; theincidence does not seem to depend on the experience ofthe operator. Thus PTCA should not be attemptedunless immmediate surgical help is available; it shouldbe tried only in patients who would otherwise betreated surgically; and patients should be monitoredfor 24 hours, preferably in a coronary-care unit, aftersuccessful dilatation. The principal late complicationof angioplasty is restenosis, but stenoses can usually bedilated more easily on the second than on the firstoccasion. Of 514 patients with successful angioplastyin one series, 171 (33%) had restenosis.10 Repeatangioplasty was attempted in 95 patients and wassuccessful in all but 3. Follow-up of 92 of theseredilated patients showed a second recurrence in only24 (26%). Hence repeat PTCA can be recommendedfor patients who have restenosis and should be

considered as an integral component ofPTCA therapy.The lower morbidity, shorter hospital stay, and

earlier return to work than after vein graft surgery makePTCA an attractive alternative to surgery, not only forpatients but also for health economists. Even withallowance for redilatation of recurrent stenoses and for

operations in failed cases, PTCA offers a saving of40-50% over elective surgery.11,12 In the United

Kingdom a coronary vein graft operation costs theNational Health Service some 3580, and the

suggested need is for 300 operations per year permillion of the population.’3 The use of angioplasty asan elective procedure for 25% of these patients couldthus save the Health Service 1:8 million annually, not tomention benefits to the patients in lower morbidity andless time off work. Another less tangible considerationis that coronary vein grafts become atherosclerotic,particularly in patients with disordered lipidmetabolism, so that 10 years after a technicallysuccessful operation most of the grafts are narrowed oroccluded. 14 For the younger patients in whom

8 Cowley MJ, Donos G, Kelsey SF, Van Raden M, Detre KM Acute coronary eventsassociated with percutaneous transluminal coronary angioplasty Am J Cardiol1984; 53: 12C-16C.

9 Cowley MJ, Dorros G, Kelsey SF, Van Raden M, Detre KM. Emergency coronarybypass surgery after coronary angioplasty. the National Heart Lung and BloodInstitutes percutaneous transluminal coronary angioplasty registry experience, AmJ Cardiol 1984; 53: 22C-26C

10 Meier B, King SB, Gruentzig AR, Tankersley R, et al. Repeat coronary angioplasty.JACC 1984; 4: 463-66.

11 Jang GC, Black PC, Cowley MJ, et al. Relative cost of coronary angioplasty and bybypass surgery in a one-vessel disease model. Am J Cardiol 1984, 53: 52C-55C.

12. Kelly ME, Taylor GJ, Moses HW, et al. Comparative cost of myocardialrevascularisation percutaneous transluminal angioplasty and coronary arterybypass surgery JACC 1985, 5: 16-20.

13 Consensus development conference: coronary artery bypass grafting. Br Med J 1984;289: 1527-29

14 Campeau L, Enjabest M, Lesperance J, et al. The relation of risk factors to the

development of atherosclerosis in saphenous-vein bypass grafts and the progressionof disease in the native circulation. A study 10 years after aorto-coronary bypasssurgery N Engl J Med 1984; 311: 1329-32.

1308

angioplasty is technically feasible, it makes good senseto have angioplasty as a first procedure and to conservethe veins for later. More recent developments in PTCAinclude its use in total coronary occlusion,15 and inacute myocardial infarction, either in conjunction withintracoronary streptokinase16 or as a primaryprocedure." Laser angioplasty is being investigated inanimals and in human cadavers but is not yet safe forclinical trial. For total occlusion not associated withinfarction, Holmes et a115 reported successful

angioplasty in 13 of 24 patients-and in 13 (68%) of 19patients in whom occlusion was believed to be of lessthan 12 weeks’ duration. Preliminary results from onecontrolled trial suggest that PTCA is superior to

intracoronary streptokinase;18 but, even if it does proveto be an effective treatment for coronary thrombosis

leading to acute myocardial infarction, logisticdifficulties will certainly prevent widespreadapplication for this purpose. As an elective treatment,however, PTCA is here to stay, and will form anincreasingly important part of the workload for allinvestigating cardiological and cardiac surgical units.

Dietary Potassium and HypertensionPOTASSIUM supplements thrive on controversy. As

lately as 1982 Kassirer’ was unable to say whether therisks of potassium salts and hyperkalaemia balancedthe risk of hypokalaemia. Shortly after, Kaplan2 arguedthat concern about hypokalaemia was appropriate andincluded reference to his study, now published,3showing that in patients with hypertension potassiumsupplements not only improve diuretic-induced

hypokalaemia but also lower the blood-pressure. In sodoing he highlighted another longstandingcontroversy; is potassium important in the

epidemiology of hypertension?Several investigators have suggested that a high

potassium diet may have an antihypertensive effect,particularly in Japan where the traditional diet is highin salt. One group showed that blood-pressurecorrelated inversely with potassium excretion anddirectly with the urinary Na+ /K+ ratio.4 Another

15. Holmes DR, Vliestra RE, Reeder GS, et al. Angioplasty in total coronary arteryocclusion. JACC 1984; 3: 834-39.

16. Gold HK, Cowley MJ, Palacois IF, Vetrovec GW, Atkins CW, Black PC, LeinbachRC Combined intracoronary streptokinase infusion and coronary angioplastyduring acute myocardial infarction. Am J Cardiol 1984; 53: 122C-125C

17. Hartzler GO, Rutherford BD, McConahy DR. Percutaneous transluminal coronaryangioplasty: application for acute myocardial infarction. Am J Cardiol 1984; 53:117C-21C.

18 O’Neill WW, Lai PY, Gangadharan V, et al Preliminary report of a randomizedprospective clinical trial of intracoronary streptokinase versus coronary angioplastytherapy of acute myocardial infarction JACC 1985; 5: 494.

1. Harrington JT, Isner JM, Kassirer JP. Our national obsession with potassium. Am JMed 1982; 73: 155-59.

2. Kaplan NM. Our appropriate concern about hypokalaemia. Am J Med 1984; 77: 1-4.3 Kaplan NM, Carnegie A, Raskin P, Heller JA, Simmons M. Potassium

supplementation in hypertensive patients with diuretic-induced hypokalaemia. NEngl J Med 1985; 312: 746-49

reported on two villages in Northern Japan that hadsimilar salt intakes but different blood-pressures:5 thevillagers with lower blood-pressure ate much morepotassium. Surveys of mixed groups of normotensiveand hypertensive Americans have also revealed a

negative correlation between blood-pressure and

potassium excretion.6 But other investigations have notshown a relation between blood-pressure and dietarypotassium.7,8More than 50 years ago Addison,9 and later

Priddle,1O suggested that a high potassium diet had anantihypertensive effect in man. Lately there has beenrenewed interest in their observation. Potassium

supplements have little’ or noI2,13 effect in men withnormal blood-pressure but in hypertensive patientsseveral groups3,14-17 report significant falls in blood-

pressure despite, with one exception,’8 a constant

sodium intake. Not all the evidence, however, pointsthis way. New Zealand workers, in a careful study,"observed no fall in the blood-pressure of hypertensivepatients in response to moderate sodium restrictionand additional potassium. Also, much of the animalwork showing a hypotensive effect from potassium hasbeen in rats with salt-sensitive hypertension;"hypertensive dogs’ and sheep22 do not respond.

4. Yamori Y, Kihara M, Nara Y, Ohtaka M, Hone R, Tsunematsu T, Note SHypertension and diet Multiple regression analysis in a Japanese farmingcommunity. Lancet 1981; i: 1204-06

5. Sasaki N High blood pressure and the salt intake of the Japanese. Jp Heart J 1962; 3:313-16.

6. Langford HG. Dietary potassium and hypertension: epidemiologic data. Ann InternMed 1983; 98: 770-72.

7 Dawber TR, Kannel WB, Kagan A, Donabedian RK, McNamara PM, Pearson G.Environmental factors in hypertension In: Stamler J, Stamler R, Pullman TN, eds.The epidemiology of hypertension New York Grune & Stratton, 1967. 255.

8. Tuomilehto J, Karppanen H, Tanskanen A, Tikkanen J, Vuori J. Sodium andpotassium excretion in a sample of normotensive and hypertensive persons inEastern Finland. J Epidemiol Commun Health 1980, 34: 174-78

9. Addison W The uses of sodium chloride, potassium chloride, sodium bromide andpotassium bromide in cases of arterial hypertension which are amenable to

potassium chloride. Can Med Assoc J 1928; 18: 281-85.10. Priddle WW. Observations on the management of hypertension Can Med Assoc J 1931;

25: 5-8.11. Khaw KT, Thom S. Randomised double-blind cross-over trial of potassium on blood

pressure in normal subjects Lancet 1982; ii: 1127-2912. Skrabel F, Anbock J, Hortnagl H, Braunsteiner H Effect of moderate salt restriction

and high potassium intake on pressor hormones, responses to noradrenaline andbaroceptor function in man. Clin Sci 1980; 59: 157s-60s.

13. Burstyn P, Hornall D, Watchorn C. Sodium and potassium intake and blood pressure.Br Med J 1980; 281: 537-39

14. Iimura O, Kijima T, Kikuchi K, Miyama A, Ando T, Nakao T, Takigami Y. Studies onthe hypotensive effect of high potassium intake in patients with essential

hypertension. Clin Sci 1981; 61: 77s-80s.15. MacGregor GA, Smith SJ, Markandu ND, Banks RA, Sagnella GA. Moderate

potassium supplementation in essential hypertension. Lancet 1982; ii: 567-7016. Smith SJ, Markandu ND, Sagnella G, Poston L, Hilton PJ, MacGregor GA. Does

potassium lower blood pressure by increasing sodium excretion? A metabolic studym patients with mild to moderate essential hypertension. J Hypertens 1983; 1 (suppl2): 27-30

17. Overlack A, Muller H-M, Kolloch R, Ollig A, Moch B, Kleinmann R, Krück F,Stumpe K. Long-term anti-hypertensive effect of oral potassium in essentialhypertension. J Hypertens 1983; 1 (suppl 2): 165-7

18. Parfrey PS, Vandenburg MJ, Wright P, Holly JMP, Goodwin FJ, Evans SJW,Ledingham JM. Blood pressure and hormonal changes following alteration indietary sodium and potassium in mild essential hypertension. Lancet 1981; i: 59-63

19. Richards AM, Nicholls MG, Espiner EA, Ikram H, Maslowski AH, Hamilton EJ,Wells JE Blood pressure response to moderate sodium restriction and to potassiumsupplementation in mild essential hypertension Lancer 1984, i: 757-61

20. Dahl LK, Leitt G, Heme M. Influence of dietary potassium and sodium potassiummolar ratios on the development of salt hypertension J Exp Med 1972; 136: 318-30

21. Young DB, McCaa RE, Pan Y, Guyton AC The natriuretic and hypotensive effects ofpotassium Circ Res 1976; 38 (suppl 11) 84-89

22. Scoggins BA, Coghlan JP, Denton DA, Fitzgerald M, Graham WF, Mason RT,Schneider EG. Haemodynamic effects of increasing extra cellular potassiumconcentration in ACTH-induced hypertension in sheep. Clin Sci 1980, 59:373s-76s