Download Clinical characteristics and prognosis significance of bundle

Clinical characteristics and prognosis significance
of bundle-branch block (BBB) associated with
acute myocardial infarction (AMI).
Toporan Daniela
Clinic of Internal Medicine and Cardiology, Emergency Hospital "Saint Pantelimon",
Bucharest, Romania.
ABSTRACT
Introduction: Left and right BBB (LBBB and RBBB) represent an independent predictor of poor outcome in
AMI.
Objective: To assess the incidence, clinical meaning and evolution of patients with BBB, left and right and
AMI.
Material and Methods: Retrospective study included 1020 patients with AMI, from which 104 (10,2%)
associated BBB at onset, respectively: 62 cases (59%) AMI and left BBB and 42 cases (41%) AMI and right
BBB. Average age was 64,5 years and male gender was more frequently (69%). 6 patients from each group
received thrombolysis with Streptokinase, respectively 9,6% in AMI and left BBB group and 14,2% in AMI and
right BBB group. We investigated for each lot with BBB, compared to standard lot the in-hospital mortality rate
and the incidence of other major cardiovascular events: ventricular dysfunction, arrhythmias, recurrent
ischemia and mechanical complications. We also analyzed the correlation between the infarct -related artery
and the presence of BBB.
Results: Compared to the patients without BBB, those with BBB were older (70±7 years) and had a more
prevalent history of diabetes, angina, myocardial infarction and heart failure.
Particularly, IMA and BBB group had a high degree of ventricular dysfunction (KILLIP class III and IV in 64
cases - 61,5%), without coronary pain. Patients with BBB, especially left BBB were admitted with a longer
interval from the onset of the symptoms (8,9 versus 5,7 hours, on average -p<0.001) and received in a lower
rate thrombolytic therapy compared to group without BBB (12% versus 34% -p<0.001). Patients with AMI and
BBB had a lower ejection fractions (average 42%, versus 51% -p<0.001) and a higher peak creatine
phosphokinase levels (2245 versus 1190 U/l -p<0.001), as a marker of necrosis severity. First class AMI after
Topol and Van de Werf determined in our study group the highest mortality (left anterior descending infarcts
accounted for 56% of the BBB and AMI cases anathomopathological analyzed, versus 38% in standard lot p<0.001). In patients with left or right BBB the rate of in-hospital death was similar (29% and, respectively
28%), but significant greater than in patients without BBB (18%) -p<0.001.
Discussion: As ECG is a poor predictor of AMI in patients with acute cardiac symptoms and LBBB , the
thrombolytic therapy should be initiated immediately in patients with ischemic chest pain suggestive of AMI
and LBBB at presentation.
The BBB seems to be a stronger predictor in the short-term prognosis of patients with AMI (in-hospital death),
compare with those without BBB.
The presence of BBB on the onset of AMI could be an independent marker of a larger, anterior infarction.
An important limit of our study is that we were unable to determine timing of onset or persistence BBB, so we
can't confirm or comment the importance and the significance of a new or a preexisting BBB.
Conclusions: Patients with BBB and AMI are less likely to receive thrombolytic therapy, associate more
frequently severe heart failure and have an increased risk for in-hospital death. No clinically significant
differences in the development of recurrent ischemia, angina or mechanical complications were seen between
patients with and patients without BBB.
INTRODUCTION
Previous studies of patients with AMI and BBB, left and right (LBBB and RBBB) at hospital admission, both in
prethrombolytic [1,2] and thrombolytic era [3-9] , have reported in general a poor overall prognosis and a high
risk for short-term death. Complete BBB, left or right, on electrocardiogram at presentation occurs in a wide
range of 1% to 15% of patients with AMI and represents an independent and very important predictor of inhospital complications and poor survival for the most investigators, even if some controversies still exists [4] .
In spite of current guidelines recommendations of using thrombolytic therapy in all patients with BBB and
clinical suspicion of AMI [10] , there is still unfortunately an obvious and proved under-use of thrombolytics in
these cases.
OBJECTIVES
The main objectives of this study were:
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To estimate the prevalence of BBB, left and right, in patients with AMI;
To compare the clinical and therapeutical characteristics in patients with AMI, with and without BBB on
the admitted electrocardiogram (ECG);
To assess the association of BBB with the major cardiovascular events:
¡ ventricular dysfunction;
¡ severe arrhythmias;
¡ recurrent ischemia;
¡ mechanical complications.
To determine the clinical meaning and independent association of BBB with in hospital death.
MATERIAL AND METHODS
Retrospective study included 1020 patients with AMI admitted in our clinic between 01 January 1997 and 01
January 2000. Of these, 104 (10,2%) associated BBB at onset, respectively: 62 cases (6,1%) -39 men and 23
women - AMI and LBBB, and 42 cases (4,1%) -32 men and 10 women- AMI and RBBB.
Patients were included in this study if they had BBB on the admission ECG.
We used all the following criteria for definition LBBB:
1.
2.
3.
4.
QRS duration > 120 ms in the presence of normal sinus or supraventricular rhythm;
QS or RS complex in lead V1;
broad or notched R waves in leads V5 and V6, or an RS pattern, and
R peak time ≥ 0,006 s without Q waves in lead I, V5 or V6 [11].
RBBB was coded if all the following criteria were met:
1. QRS duration > 120ms in the presence of normal sinus or supraventricular rhythm;
2. R or RSR' complex in lead V1, and
3. RS in leads I, aVL, V5, V6, with a prolonged, shallow S wave [11] .
The block was complete and persistent. Patients with incomplete, intermittent or alternating BBB on the
admission ECG were excluded from the study.
Information on "new" versus "old" BBB was not available (as the block was present on clinical admission with
no previous ECG available for review, we considered it an "indeterminate" one).
Average age was 70 years (47-93) for the patients with AMI and LBBB and 64,5 years (45-84) for those with
AMI and RBBB.
Male gender was more frequently (69%) in cases with AMI and BBB.
The diagnosis of AMI in patients with LBBB was based on the cardiopulmonary symptoms or signs (of these,
typical chest pain was found in 38,5% cases -24 patients), and at least one of the following criteria:
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enzymatic: total creatine kinase at least twice the upper limit of the normal range, in all patients (100%);
electrocardiographical (ECG) evidence of AMI, in 20% of cases (12 patients);
alternative echocardiographical (in 60% of cases -37 patients) or autopsy evidence (15% of cases -10
patients).
We used the Sgarbossa et al. algorithm in order to identify the patients with AMI in the presence of LBBB
[12] .
This scoring system defined the ECG finding as positive (suggestive of AMI) if it scored ≥ 3 points based on
three criteria:
1. ST-segment elevation ≥ 1 mm and concordant with QRS complex (score 5);
2. ST-segment depression ≥ 1mm in lead V1,V2 or V3 (score 3) and
3. ST-segment elevation ≥ 5mm and discordant with QRS complex (score 2).
Six patients from each group with BBB received intravenous thrombolysis with streptokinase (1,5 M.U.within
60 min.), in the first 12 hours since the onset of symptoms, respectively 9,6% in AMI and LBBB group and
14,2% in AMI and RBBB group, compared with 34% in control group.
The primary end point of the study was in hospital mortality. The secondary end points were in-hospital
cardiovascular events, others than death: ventricular dysfunction, arrhytmias, recurrent ischemia or angina,
congestive heart failure, cardiogenic shock, second- or third degree heart block, mechanical complications
and cardiac arrest, and the correlation between the infarct-related artery in the presence of BBB.
Others predictor variables included cardiovascular history (prior MI, angina, congestive heart failure, stroke),
cardiac risk factors (diabetes mellitus, hypertension, current cigarette smoking, dyslipidemia), chest pain on
admission, severity of presentation (Killip class, AMI location), interval between symptom onset and in hospital
admission, using of intravenous thrombolytic therapy, reason for non using thrombolytics (non diagnostic
ECG, advanced age, duration of symptoms, others).
Statistical analysis was based on the Student t-test for continous variables and the chi-square test for
proportions.
p values < 0,001 were considered statistically significant.
RESULTS
Baseline patient characteristics are listed in Table 1.
Compared with patients without BBB, those with BBB were older (70±7 years) and had a more prevalent
cardiovascular history of angina, myocardial infarction, heart failure and cardiac risk factors: diabetes mellitus
and hypertension.
Particularly, at presentation, AMI and BBB group had more frequently severe congestive heart failure (Killip
class III and IV), in 61,5% of cases and no coronary pain, while chest pain was more common in patients
without BBB (68,7% of cases) (p< 0.001).
Patients with BBB, especially LBBB were admitted with a longer interval from the onset of the symptoms (8,9
versus 5,7 hours, on average - p< 0,001) and fewer patients with BBB than patients with no BBB received
thrombolytic therapy (12% versus 34%, p<0,001).
The location of MI at presentation was more frequently reported as "unspecified" in patients with LBBB
(68,0%) or RBBB (43,1%) compared with patients without BBB (31,5%) (p< 0,001).
Of cases with BBB, the most frequent MI location was anterior wall; this association was particularly strong for
patients with RBBB.
Patients with AMI and BBB had a higher peak creatine phosphokinase levels (2245 versus 1190 U/l - p<
0,001) as a marker of necrosis severity and a lower discharge ejection fraction ( on average 42%, versus 51%
- p< 0,001).
In patients with left or right BBB the in-hospital death rate was cvasi similar (29% and, respectively 28%), but
significant greater than in patients without BBB (18%) (p< 0,001) (Table 2).
There were 18 deaths of 62 cases with AMI and LBBB (none of those who received thrombolysis) and 12
deaths of 42 cases with AMI and RBBB (2 of those thrombolysed).
Cases with AMI and BBB had more frequently cardiovascular events during the hospitalization period,
especially congestive heart failure, cardiogenic shock and cardiac arrest which represented also the most
common causes of death (Table 3). No significant differences were remarked regarding the angina, recurrent
ischemia and malignant ventricular arrhytmias between the analyzed groups.
Of 26 death cases anathomopathological studied, first class AMI (after Topol and Van de Werf classificationTabel 4) [13] was dominant and determined the highest mortality (the culprit lesion in the left anterior
descending coronary artery accounted for 56% of the AMI and BBB cases, versus 38% in standard lot -p<
0,001) (Table 5).
DISCUSSION
In our study the prevalence of BBB on admission ECG of patients with AMI was, on average, 10% of cases.
The risk for in-hospital mortality was equally high for patients with LBBB and RBBB at presentation (29% and,
respectively 28%), compare with patients without BBB (18%).
Patients with AMI and BBB were older and with more frequently severe heart failure than chest pain on
admission, but even when they were matched with control group for age and Killip class, BBB remained an
independent predictor of mortality.
The presence of BBB is still associate with a poor outcome, even in thrombolytic era.
In our study thrombolytic therapy was underutilized in patients with AMI and BBB for two main reasons:
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Those who presented without chest pain were at greater risk of undertreatment;
ECG was frequently undiagnostic in cases with LBBB and acute cardiopulmonary symptoms (only 20%
of our patients benefited of the Sgarbossa diagnostic algorithm).
Patients with BBB, especially RBBB, seem to have more larger anterior infarcts than their control subjects and
this fact was confirmed also by our anathomopathological findings.
The severe ventricular dysfunction (lower ejection fraction), cardiogenic shock and cardiac arrest were more
frequent among patients with AMI and BBB during hospitalization.
Study limitations: Our analysis was a retrospective one and included a relative small number of patients. We
couldn't determine timing of onset or persistent BBB, if "new" or "old", so we can't appreciate the importance
and the influence of this factor on patients prognostic and we can't confirm or comment the significance of a
new or a preexisting BBB.
This study was limit to the hospitalization period, so the conclusions regard only the short-term outcome of
patients.
We had not the possibility of an angiographical study for the patients.
The message of the study is that in elderly patients with atypical presentations, particularly severe heart
failure and with BBB, the suspicion of AMI has to be seriously take into account and, in the absence of
contraindications, the reperfusion therapy should be urgently consider because of the short-term high
mortality risk.
CONCLUSIONS
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The prevalence of BBB, left or right, in patients with AMI was, on average, 10% of cases.
The presence of BBB on AMI onset represented an independent and strong predictor of poor outcome
and was associated with a high risk of in hospital death rate, compare with control group (29% versus
18%).
Patients with BBB and AMI had more frequently severe heart failure, were less likely to be diagnosed
with MI and less likely to receive thrombolytic therapy in time.
Clinical evolution was complicated more often with cardiogenic shock and cardiac arrest in patients
with BBB. No clinically significant differences in the development of recurrent ischemia, angina,
advanced degree heart block, or mechanical complications were seen between patients with and
without BBB.
In patients with BBB and atypical presentation it is important first to think about a possible AMI
diagnosis and, in the absence of contraindications, to administrate thrombolytiv therapy in cases with
strong clinical suspicion.
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