Isolated Obstruction of the Right Coronary Artery

Isolated Obstruction of the Right Coronary Artery* A. Bakst, M.B.; B. S . Lewis, M.B.; A. S . Mitha, M.B.; and M . S . Gotsman, M.D. Twelve patients with isolated narrowing (70 percent or more) or complete obstruction of the right coronary artery were studied. Five patients had subtotal occlusion, and only one had evidence of infarction. Seven patients had complete obstruction of the right coronary artery: one had good collateral circulation, a normal resting electrocardiogram (ECG) and ventriculogram; four had clinical, ECG and ventriculographic evidence of infarction, but the asynergy was relatively localized and part of the diaphragmatic surface of the left ventricle had been protected by a normal circumflex artery with important posterolateral branches. The other two patients, with a small circumflex artery, had extensive ECG changes and diaphragmatic asynergy.

nowledge of the natural history of coronary artery disease is based o n serial historical, electrocardiographic, coronary angiographic and postmortem studies. Isolated disease of the right coronary artery ( RCA) is rarely found at autopsy in patients who die from coronary artery disease (CAD).IB Patients with single-vessel CAD are usually younger, have mild or atypical angina pectoris of short duration, and those with RCA obstruction often have angina pectoris as well as a history of myocardial infarction. The severity of angina depends on a critical reduction of the coronary arterial blood flow: while this is usually associated with extensive triple or quadruple vessel disease, occasional patients with single-vessel disease and 90-95 percent obstruction and a very small blood flow through the affected artery may have a similar clinical syndrome.'e8 Collateral vessels do not protect the heart from myocardial infarction if an artery is o c c l ~ d e d The . ~ ~ ~electrocardiogram ( ECG ) often predicts the area of asynergy as this is related to occlusion or narrowing of the artery supplying the affected territory.I0 However, despite the extensive literature, the ECG and ventriculographic pattern in a defined pathologic lesion of the RCA in the individual patient is still unclear ( Table 1 , 2 ) .7-23 This paper is part of a prospective in-depth study of coronary artery disease based on roronary angi0graphy during life' It with One pathologic entity or set: the clinical, electrocardiographic, hemodynamic and venticulographic patterns in a group of 12 patients with significant narrowing or

total obstruction of the right coronary artery. We analyzed the coronary arteriographic patterns in a consecutive group of 200 patients. Ninety-five percent of the patients had important angina pectoris and were studied as a prelude to operation, or with chest pain resembling angina pectoris and in whom coronary angiography was undertaken to exclude CAD. The other 5 percent were young patients with previous myocardial infarction or an abnormal ECG. Twelve patients had significant single-vessel disease with narrowing of 70 percent or more or complete occlusion of the right coronary artery. We have arbitrarily selected a 70 percent obstruction of a coronary artery to be of functional significance: lesser degrees of narrowing were considered not significant.24 Patients with significant obstruction of other arteries were excluded from this study, although four patients had atheroma of another artery (or arteries); two had minor atheroma of both other arteries; one had a 50 percent and the

Table 1-Pertinent Literature Relating t o Coronary Artery Disease Demonstrated b y Postmortem Studies No. of Cases

Author

Comment

Ssphir. Priest, Hamburger, et al (1935)'

34

no patient with infarction who died had aingle VWI diseane

Blumgart. Schleainger & Davis (1940)'

30

4 c a m of single RCA occlusion (100%)

Blumm* Schleainger & Zdl (19.41)'

365

Snow, MormnJones &

25

1 died of acute infarction. 2 hnd angina pectoris & 1 had associated hypertension & cirdiac failure result of coronary dieease depends on underlying coronary anatomy

syndrome of single v e l occlusion is n d described dm not discus. sinplc-V-l

o~ruction &

its clinical counterprt coronary artmy occlusion leads to infarction. collaterals develop later but do not develop with urndual nnrrowing to prevent infarction

h b e r (1965)'

'From the Cardiac Unit, Wentworth Hospital and the University of Natal, Durban, South Africa. Manuscript received December 18, 1972; revision accepted

Fultm ( I 9 6 5 ) b

25

Reprint reqtrests: Dr. Gotsman, Wentworth Hospital, PO Jacobs, Durban, South Africa

I case of ainple RCA d k was wansociated with paaterior infarction & myocardial rupture

James (1gBS,6

-

RCA is artery of arrhythmias & sudden death

111np7. ..

18

CHEST, VOL. 65, NO. 1, JANUARY, 1974

ISOLATED OBSTRUCTION OF RIGHT CORONARY ARTERY Table %Pertinent

19

Literature Relating to Coronary Artery Diseaae Demonstrated b y Coronary Angiography During Life

Author

No. Caaes

Comment

Lioff, Kasparian, Segal, et al (1965)18

70

does not describe syndrome of angle coronary obstruction anaatomotic channels did not develop until artery was completely occluded

Parker, Di Giorgi & Weat (1966)17

88

4 patients with angle veml coronary artery disease

Bjork, Cullhed & Hallen (1967)M

52

8 patients had more than 50% narrowing of right coronary artery only ECG: normal, 2; ischemia or LBBB, 4; anterior infarction, 2; inferior infarction, 0 left ventricular angiogram: normal 4; abnormal movement 4;-posterior wall, 2; apical, 1; anterior, 1

Diethrich, Liddicoat, Kinard, et a1 (1967)21

313

58 patients had angle-vessel disease; 23 (39%) had right coronary artery d k m (<75% narrowing) of 23, 14 had total & 9 had subtotal (75% or more) obstruction diaphragmatic ischemia occurred if right coronary artery was dominant

Hultgren, Calciano, Platt, et a1 (1967)=

55 32 patients

angina was rare in presence of single-vesael coronary artery disease only 1 patient bad isolated right coronary artery narrowing

Proudfit, Shirey & Snnea (1967)'

1 (274 normal subjects, 726 patients in whom 588 had obstruction of at least 50% of lumen)

199 patients (34%) had aingle vesael d i i , with narrowing of more than W o ; of these, 62 had iaolated narrowing of RCA RCA diseaae could cause any clinical syndrome patients conaidered to have noncoronary symptoms or atypical angina had high incidence of single-vessel disease if coronary leaions were demonstrated predominant angle-vessel severe obstruction was common in patients who had mymardial infarction, especially in abaence of angina pectoria, & in thoae who had rest pain only complete RCA obstruction was more common than LAD obstruction when angina pectoris occurred in association with myocardial infarction

Gensini & Buonanno (1968)23

6 patients had isolated atheroma, narrowing or obstruction of right coronary artery leaions occurred at any site, often with good collateral circulation & distal filling of artery was often present clinical symptoms of coronary artery disease were usually associated with multiple-vessel disease electrocardiogram underestimated severity of coronary artery disease

McConahay, McCalliater, Hallermann, et al (1970)10

84 patienta had disease of right coronary artery (more than 50% narrowing); 10 had no other cardiac disease duration of history of angina was uaually less than 3 years of 10 patients without other kinds of cardiac disease, only 3 had an infarct pattern on ECG or VCG severe disease of right coronary artery (single or multiple) was associated with greater frequency of detectable infarcts than severe dieease of left anterior descending artery 8 of 15 patients with angle right coronary artery narrowing (subtotal or total) had collateral vessels

Helfant, Vokonas & Gorlin (1971)O

119 cacres of angle-vessel coronary artery disease only (greater than 90% narrowing)

50 patients (41%) had isolated narrowing or obstruction of right coronary artery 30 patients with right coronary artery disease had collaterals (of 61 patients with collateral vessels); 20 had no collaterals (of 58 patients) in comparison of groups of patients with & without collaterals, there was no difference in level of previous phyeical activity, duration of angina pectoris, hiatory of infarction or both; they had identical ECG & hernodynamic data collateral circulation was thought to improve prognosis

other patient had a 80 percent narrowing of t h e left anterior descending artery ( Table 4 ) . T h e r e was routine physical examination of each patient. A standard 12-lead ECC was recorded a n d was repeated after effort if t h e tracing was normal, using a constant load bicycle ergometer a n d a triangular effort test. Patients were exercised in a sitting position a t a workload of 25 watts for three minutes, a n d t h e load was increased every three minutes until t h e onset of angina or fatigue.25 Posteroanterior a n d lateral chest radiographs were taken a t a standard 6-foot tubefilm distance. T h e coronary circulation a n d ventricular function of each patient was analyzed in detail during cardiac catheterization.

CHEST, VOL. 65, NO. 1, JANUARY, 1974

T h e details of t h e methodology a n d techniques have been described.26-28 Left ventriculography was performed in t h e right anterior oblique view. T h e left ventriculogram was analyzed a n d t h e degree of ventricular asynergy or abnormal movement was estimated.20 Ventricular volumes were measured b y t h e uniplane technique of Greene e t al.30 Selective coronary arteriography was performed b y t h e Judkins method in different oblique positions, using a 35 m m cine technique with a 6-inch image intensifier.31-34 Coronary arteriograms were analyzed for normality, site, degree a n d extent of arterial stenosis o r obstruction, t h e presence of additional nonobstructive atheromatous plaques a n d t h e pat-

BAKST ET AL Table 3--Clinical and Hemodyrurmic Data

Patient, No.

Episodes of Clinical Infarction

Angina Related to Infarct

Group 1. Subtotal occlusion of RCA 1 0 Pre

3

Pre post

2

6

Grade

Grade

Duration, mos

Systolic

24

2

1

24

174

412

73

+ 36

126

2

1

168

162

7-8

-

2

2

1

2

150

0-14

-

3 5

2 2

2

5

150

2-3

Pre post

1

Left Ventricular, Pressure, mm Hg

Duration, rnos

Group 2. Total occlusion of RCA 6 0 Pre

12

Dyspnea \

Ejection End-Diastolic Fraction, yo

and angiographic data are shown in detail in Tables 3 and 4 and summarized in Tables 5-7. The patients were men aged 40 to 56 years except for two older women. Eight patients had angina pectoris; seven of

tern of collateral circulation around and beyond an area of obstruction.

RESULTS

The clinical, electrocardiographic, hemodynamic

Table M o r r e l a t i o n Between Coronary Arteriogram, Left Ventriculogram and Electrocardiogram R i h t Coronary Artery

Patient No. Age.

Dominant Caolury

Ym Sex Artery

Group 1 . 8 u W ooduaioo d RCA 1 47 M RCA 2

10

M

RCA

Severity of Site of Narrowing, D i i l Narrowing % Vessel Collaterain

- - -

-

Left Anterior Deacending Artery

Circumflex Artery

Severity of Narrowing

Sire

Severity of Narrowing

-

-

Electrocardiogram Diaphragmatic r Asynergy Frontal Site of QRS Patholagic Site % Axis Q Waves Site of Inchemia

middle %

80

present nil

mild atheroms amall

mild atheroma nil

0

+20'

nil

positive effort test

middle %

95

present nil

single 80 %

d

nil

nil

0

+70°

nil

inferior

l

3

63

M

RCA

middle %

80

prenent nil

0

large

nil

nil

0

+70°

nil

nil

4

56

F

RCA

middle %

95

prenent nil

50%

average

nil

nil

0

f45'

nil

positive effort tent

5

51

M

RCA

proximal%

80

present from RCA 0 from LCA

amall

nil

basal%

- 0

0

Group 2. T&l onlusiw cd RCA 6 47 M RCA

2.3.aVF nil

middle%

100

present from LCA 0

very large nil

nil

7

51

M

RCA

middle %

I00

pnaent from LCA 0

very large nil

middle % I0 +W

R

61

F

RCA

proximal %

100

absent

9

53

M

RCA

middle %

100

present from RCA 0 from LCA

large

nil

basal %

10

52

M

RCA

middle %

100

p e n t from RCA 0 from LCA

average

nil

m i d d l e s I3 +BOO

2.3.aVF anterdateral

I1

56

M

RCA

middle 5j

100

absent

0

amall

nil

apical 6 30 +3O0 middle f6

2.3.aVF anterolateral

12

45

M

RCA

proximal %

100

present from LCA 0

large

nil

apical & middle %

- - 40"

2,3,aVF ankrolateral

nil

nil

mild atheroms average

mild atberoma basal f6

+30°

22 0

nil

pmitive effort test

3,aVF

nil

3.aVF

antemlateral

- +10"2.,aVF

nil

LCA-left c a w artery; RCA-right coronary artery % .synergy- % of circumference of left ventricular wall ahowing asynergy in right anterior oblique view

CHEST, VOL. 65, NO. 1, JANUARY, 1974

ISOLATED OBSTRUCTION OF RIGHT CORONARY ARTERY Table 5--Clinical Stat- of Pa8ientr with RCA h a m Clinical Findings

No. Patients

Angina pectoris

6

Tabk 7-Elcehocardiograplrie Patter- of

RCA Di.eou

Subtotal Occlusion, No.

Previous myocardial infarction

Normal ECG

Angina

Positive effort teat

+ previous myocardial infarction

Acute pulmonary edema

patient^ with

Total Occlusion, No.

Inferior iechemia

Total

Inferior infarction

Dyspnea (NYHA) Grade 1

Inferior infarction lateral ischemia

*New York Heart Association Grading6

these gave a story of antecendent infarction. The clinical duration of overt coronary artery disease ranged from 1 to 168 months. Results of physical examination were unremarkable. Patients in Group 1 (uide infra) had no abnormal physical signs, but had an intermittent Sr. The mean blood pressure was 144190 mm Hg and the serum cholesterol value was 316 mg percent (range 151-605 mg percent). Patients in Group 2 were more abnormal: three had an important "a" wave in the jugular venous pressure, two had an abnormal left ventricular impulse on palpation, one had functional mitral incompetence, two had a ventricular gallop sound, two an SI, and two were receiving digitalis. The mean blood pressure was 147190 mm Hg, and the serum cholesterol level was 219 mg percent (range 200-372 mg percent). Coronary Arteriographic Pattern

+

cent or more) of the right coronary artery: this was located in the middle third of the main artery in four and in the proximal third in one ( Fig 1) . These patients had significant angina pectoris and one also gave a story of previous infarction; the severity of angina was related to the degree of narrowing (tables 3,4). The duration of symptoms was variable and ranged from one month to 14 years. The ECG showed a pattern of myocardial infarction in one patient (who had 95 percent obstruction), resting ischemia in one and a positive effort test in two. One patient with 80 percent obstruction had a normal ECG. The ventriculograrn was normal except in the patient who had clinical and electrocardiographic evidence of infarction: he had a small area of asynergy of the basal diaphragmatic surface. Group 2: Complete Obstruction of the Right Coronary Artery The duration of the history ranged from two months to eight years. Three patients had total ob-

The patients were divided into two groups: Group 1consisted of five patients with subtotal occlusion of the right coronary artery. Group 2 consisted of seven patients with total obstruction. Group 1: Subtotal Obstruction Five patients had a subtotal obstruction (70 per-

-

Table M i t e of Ventricular A~ynergyin Patient. with RCA Direore RCA Narrowing

Normal

Subtotal

Total

4

1

Middle or baaal third of diaphragmatic swfaee Apical and middle third of diaphragmatic surface

CHEST, VOL. 65, NO. 1, JANUARY, 1974

FXCWRE 1. Right coronary arteriogram (LAOview) showing subtotal obstruction of RCA in its middle third.

BAKST ET AL

22

FIGURE2. Total obstruction of right coronary artery with large circumflex artery and collateral vessels filling posterior interventricular artery. (a, left ) Right coronary arteriogram ( RAO view ) . Total obstn~ctionof right coronary artery in its middle third. ( b, right) Left coronary arteriogram (LAO view). Posterior interventricular branch of right coronary artery fills from collateral vessels.

struction in the proximal third of the main artery, three at the junction of the proximal and middle third and one in the middle third. The outcome of total obstruction appeared to depend on the coronary artery anatomy, the dominance of the right coronary artery and the size of the circumflex artery and its branches, and the availability of important collateral vessels. From the coronary arterial pattern, the ECG and the ventriculogram it was possible to divide the patients into three subsets: 1 One patient had a history of angina but no overt episode of infarction. His ECG showed ischemia on effort, and the ventriculogram was normal. He had a large circumflex coronary artery with large posterolateral marginal branches and an excellent collateral circulation filling a

normal posterior interventricular artery. The collateral circulation had protected the myocardium from total death at the time of right coronary artery obstruction (Fig 2). 2 Four patients with a history of previous infarction had an electrocardiographic pattern of diaphragmatic infarction and asynergy of the basal and/or middle third of the diaphragmatic surface of the left ventricle. They had a normal circumflex artery with important posterolateral branches ( Fig 3 ) . 3 Two patients with previous infarction had a small circumflex artery and in one the distal vessel did not fill from collateral vessels. Both patients had large areas of asynergy, involving the entire diaphragmatic surface except the apical tip. This was reflected in the ECG, which showed diaphragmatic infarction but more important Q waves in lead 2 than patients in the previous subset showed. The ECG also showed T wave inversion in the anterolateral left ventricular leads (VI-6, Fig 4).

FIGURE 3a. Complete obstruction of right coronary artery, with normal circumflex artery and important posterolateral branches. ECG showing diaphragmatic myocardial infarction.

CHEST, VOL. 65, NO. 1, JANUARY, 1974

ISOLATED OBSTRUCTION OF RIGHT CORONARY ARTERY

FIGURE 4b. Left ventriculogram (RAO view) showing asynergy of entire diaphragmatic surface. FIGURE 3b.Left ventriculogram (RAO view) showing asynergy of middle third of diaphragmatic surface.

The right coronary artery provides the main blood supply to the right ventricle, right atrium and a variable portion of the diaphragmatic surface of the left ventricle and the interventricular septum.% The artery runs in the right atrioventricular groove. In 55 percent of patients, it gives off the artery to the sinoatrial nodee and two or three posteriorly directed branches to the right atrium. The named anterior branches are conal, right ventricular and acute marginal. The distal right coronary artery continues to the crux of the heart and gives off the posterior interventricular artery which runs in the posterior interventricular groove. A small branch, also arising at the crux, supplies the A-V node in 90

percent of patient^.^,^ We have observed that the blood supply to the proximal diaphragmatic surface of the left ventricle depends on the dominance of the right coronary artery and its interrelationship with the circumflex. These vessels are complementary: if the circumflex artery is small, branches of the terminal portion of the RCA cross the crux and supply the posterior and diaphragmatic surface of the left ventricle. Similarly, the distal surface of the diaphragmatic surface is often supplied by the distal portion of the anterior descending branch of the left coronary artery. Severe subtotal narrowing or total occlusion of the right coronary artery produces significant angina pectoris or myocardial infarction. Obstruction of the right coronary artery usually causes infarction of the basal half of the diaphragmatic surface of the left ventricle, but the extent of myocardial damage is

FIGURE 4a. Complete obstruction of right coronary artery with small circumflex artery. ECG showing diaphragmatic infarction with lateral extension and ischemia.

CHEST, VOL. 65, NO. 1, JANUARY, 1974

BAKST ET AL

variable and depends on the underlying coronary arterial anatomy and the availability of a collateral blood supply. If the circumflex artery and its posterolateral marginal branch are large, the apical third of the diaphragmatic surface is usually spared. The ECG reflects the degree of myocardial dysfunction and asynergy as assessed at ventriculography. It is interesting that no patient in this series had a disturbance of atrioventricular conduction. Our data provide no information about the natural history i f this particular disorder, and the duration of symptoms range from 1 to 168 months. Disease of the right coronary artery may be compatible with long survival if the other vessels are normal.

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1

k

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