The presence of syncope despite medical therapy in patients with hypertrophic cardiomyopathy (HC) is considered an indication for surgical myectomy; however, no study has examined the long-term effects on recurrent syncope and survival after surgery in these patients. We examined 239 patients with HC and a history of syncope who had undergone surgical myectomy (mean age 48 ± 17 years; 56% men). The patients were age- and gender-matched to patients with HC and syncope who were treated medically without myectomy (mean age 51 ± 16 years; 59% men). The median follow-up period was 4.7 years (0.8, 11.3). The recurrence rate of syncope was 11% in the myectomy patients and 40% in the medical group (p <0.0001). Multiple episodes of syncope, left ventricular outflow tract obstruction, and recent syncope were identified as baseline predictors of recurrent syncope. Survival free of all-cause mortality was greater for patients who had undergone surgical myectomy than for the medically treated patients (10-year estimate 82 ± 4% vs 69 ± 4%; p = 0.01). In conclusion, surgical myectomy in patients with HC and a history of syncope was associated with a reduction in recurrent syncope and increased survival.
Surgical septal myectomy is a low-risk procedure that effectively treats drug-refractory symptoms of angina and dyspnea in patients with obstructive hypertrophic cardiomyopathy (HC). Studies with extensive follow-up (>10 years) have found survival after myectomy to be comparable to that of the general population. The presence of syncope despite medical therapy is considered an indication for myectomy ; however, no study has examined the long-term effects on recurrent syncope and survival after surgery in these patients. The aim of the present investigation was to examine the effect of myectomy on morbidity and mortality in patients with HC and syncope.
Methods
The institutional review board at Mayo Clinic approved the present investigation. A retrospectively assembled cohort of patients (n = 239) who were evaluated at the Hypertrophic Cardiomyopathy Clinic at Mayo Clinic (Rochester, Minnesota) from August 1962 to February 2010 were enrolled in the present study. The inclusion criteria were (1) a diagnosis of HC; (2) a history of syncope; (3) surgical septal myectomy performed at Mayo Clinic; (4) the absence of previous sudden cardiac death (SCD) or appropriate automated implantable cardioverter-defibrillator (AICD) discharge for treatment of lethal arrhythmia; and (5) informed consent for the use of the medical record for research purposes. For comparison, the same clinical criteria were used to identify an age and gender-matched cohort (1:1 matching; n = 239) of patients with HC who had experienced syncope but did not undergo surgical myectomy.
The diagnosis of HC was made in the setting of typical myocardial hypertrophy in the absence of local or systemic etiologies. Left ventricular outflow tract (LVOT) obstruction was defined as an LVOT gradient ≥30 mm Hg at rest. Syncope was defined as the sudden, complete loss of consciousness with an associated failure of postural tone and subsequent recovery. Patients underwent septal myectomy using surgical techniques previously described in detail.
Symptoms, clinical events, and vital status were ascertained by mailed questionnaire, telephone interview, interrogation of the Social Security Death Index, and a detailed review of the medical record. HC-related mortality included deaths from heart failure, stroke, perioperative deaths, HC-related pulmonary hypertension, and SCD. SCD was defined as instantaneous, unexpected death within 1 hour in those previously in a stable condition or nocturnal death in those with no history of worsening symptoms. Successful resuscitation from cardiac arrest and appropriate AICD discharges for treatment of lethal arrhythmia, including overdrive pacing for sustained ventricular tachycardia, were considered SCD.
The Kaplan-Meier method was used to estimate the rates of survival (± SE) from the end points of all-cause mortality, HC-related mortality, and SCD at 10 years of follow-up (JMP, version 8.0, SAS Institute, Cary, NC), and the log-rank test was used to formally compare these rates between the surgical myectomy and medically treated groups. The follow-up duration was calculated from septal myectomy for the surgical group and the initial clinical evaluation for the medically treated patients. All data are presented as mean ± SD, median (25th and 75th percentiles), or count (percentages), as noted. Variables were compared using 2-sample t tests, chi-square tests, log-rank tests, or Wilcoxon rank sum tests, as appropriate. Chi-square tests were used to compare the variables associated with recurrent syncope during follow-up, because available data did not permit a time-to-event analysis.
Multivariate analyses of mortality end points (i.e., all-cause mortality, HC-related mortality, and SCD) at 10 years of follow-up were constructed using the Cox proportional hazard regression method, with variables included in the model if the univariate associations achieved p ≤0.10 and/or were thought to be clinically appropriate (e.g., age, gender). The variables in the model are reported as hazard ratios, with 95% confidence intervals.
Results
During the study period, 1,624 patients underwent surgical septal myectomy for HC. Of these, 239 (15%) met the study inclusion criteria and were subsequently matched to an equal number of patients with HC and a history of syncope who were treated medically. Table 1 lists the baseline characteristics of the study population. Among the patients who underwent surgical myectomy, severe symptoms of dyspnea, LVOT obstruction, previous pacemaker or AICD, more intensive medical therapy, and younger age were more common than in the medically treated group ( Table 1 ). No significant difference was seen in the prevalence of recorded medical co-morbidities between the 2 groups. Details regarding the characteristics and timing of syncope in both cohorts are listed in Table 2 .
| Variable | Total Population (n = 478) | Myectomy (n = 239) | Medical Therapy (n = 239) | p Value |
|---|---|---|---|---|
| Age (yrs) | 50 ± 17 | 48 ± 17 | 51 ± 16 | 0.03 |
| Male gender | 274 (57%) | 134 (56%) | 140 (59%) | 0.6 |
| Family history of sudden death ∗ | 51 (11%) | 29 (12%) | 22 (9%) | 0.3 |
| Canadian class III-IV angina | 58 (12%) | 33 (14%) | 25 (11%) | 0.3 |
| New York Heart Association class III-IV dyspnea | 188 (39%) | 126 (53%) | 62 (26%) | <0.001 |
| Nonsustained ventricular tachycardia † | 78 (29%) | 42 (33%) | 36 (26%) | 0.2 |
| Septal thickness (mm) ‡ | 21 ± 6 | 21 ± 7 | 20 ± 6 | 0.8 |
| Left ventricular outflow tract obstruction at rest (≥30 mm Hg) | 223 (47%) | 173 (72%) | 50 (21%) | <0.001 |
| Left ventricular outflow tract gradient (mm Hg) § | 38 ± 37 | 55 ± 38 | 20 ± 25 | <0.0001 |
| Atrial fibrillation | 72 (15%) | 34 (14%) | 38 (16%) | 0.6 |
| Stroke | 20 (4%) | 9 (4%) | 11 (5%) | 0.7 |
| Heart failure | 33 (7%) | 17 (7%) | 16 (7%) | 0.9 |
| Diabetes | 28 (6%) | 10 (4%) | 18 (8%) | 0.1 |
| Hypertension | 125 (26%) | 68 (29%) | 57 (24%) | 0.2 |
| Automated implantable cardioverter-defibrillator | 40 (8%) | 27 (11%) | 13 (5%) | 0.02 |
| Pacemaker | 52 (11%) | 34 (14%) | 18 (8%) | 0.02 |
| Medications | ||||
| β Blocker | 300 (63%) | 184 (77%) | 116 (49%) | <0.0001 |
| Calcium channel blocker | 152 (32%) | 93 (39%) | 59 (25%) | 0.0008 |
| Disopyramide | 32 (7%) | 23 (10%) | 9 (4%) | 0.009 |
| Amiodarone | 20 (4%) | 13 (6%) | 7 (3%) | 0.2 |
∗ Family history of sudden death unknown for 4 patients because they were adopted.
† Holter data available for 128 myectomy patients and 138 nonmyectomy patients.
‡ Septal thickness available for 239 myectomy patients and 228 nonmyectomy patients.
§ LVOT gradient available for 237 myectomy patients and 216 nonmyectomy patients.
| Variable | Total Population (n = 478) | Myectomy (n = 239) | Medical Therapy (n = 239) | p Value |
|---|---|---|---|---|
| Syncope at initial presentation | 224 (47%) | 81 (34%) | 143 (60%) | <0.0001 |
| Syncope onset <6 months before evaluation | 109 (23%) | 53 (21%) | 56 (23%) | 0.74 |
| Most recent syncope <6 months before evaluation | 205 (43%) | 95 (40%) | 110 (46%) | 0.17 |
| Recurrent syncope | 287 (60%) | 153 (64%) | 134 (56%) | 0.08 |
| Syncope during medical therapy | 325 (68%) | 197 (82%) | 128 (54%) | <0.0001 |
| Exertional syncope | 201 (42%) | 118 (49%) | 83 (35%) | 0.0012 |
| Presyncope | 321 (67%) | 183 (77%) | 138 (58%) | <0.0001 |
| Neurocardiogenic syncope | 63 (13%) | 26 (11%) | 37 (16%) | 0.14 |
The median follow-up for the entire cohort (n = 478) was 4.7 years (0.8, 11.3). The patients who underwent septal myectomy had a significantly lower incidence of recurrent syncope during follow-up than the medical group (11% vs 40%, p <0.0001). This relationship remained after restricting the analysis to only those patients with LVOT obstruction at rest. Among the baseline predictors of recurrent syncope during follow-up were a history of multiple episodes of syncope (>1 episode), LVOT obstruction, and recent syncope (<6 months before the index date; Table 3 ).
| Variable | Total Population (n = 478) | Recurrent Syncope | p Value | |
|---|---|---|---|---|
| Yes (n = 123) | No (n = 355) | |||
| Myectomy | 239 (50%) | 27 (11%) | 212 (89%) | <0.0001 |
| No myectomy | 239 (50%) | 96 (40%) | 143 (60%) | |
| Age (yrs) | 50 ± 17 | 49 ±17 | 50 ± 17 | 0.5 |
| Female gender | 204 (43%) | 47 (23%) | 157 (77%) | 0.2 |
| Last syncope within 6 months of index | 205 (43%) | 71 (35%) | 134 (65%) | 0.03 |
| First syncope within 6 months of index | 109 (23%) | 28 (26%) | 81 (74%) | 0.99 |
| Presyncope | 321 (67%) | 95 (30%) | 226 (70%) | 0.005 |
| History of neurocardiogenic syncope | 63 (13%) | 24 (38%) | 39 (62%) | 0.02 |
| History of recurrent syncope before index date | 287 (60%) | 106 (37%) | 181 (63%) | <0.0001 |
| Syncope during medical therapy | 325 (68%) | 103 (32%) | 222 (68%) | <0.0001 |
| Atrial fibrillation | 72 (15%) | 19 (26%) | 53 (74%) | 0.9 |
| Hypertension | 125 (26%) | 25 (20%) | 100 (80%) | 0.08 |
| Heart failure | 33 (7%) | 21 (64%) | 12 (36%) | 0.2 |
| Diabetes | 28 (6%) | 7 (25%) | 21 (75%) | 0.9 |
| Left ventricular outflow tract gradient >30 mm Hg at rest | 223 (47%) | 43 (19%) | 180 (81%) | 0.002 |
| Septal thickness (mm) | 20 ± 6 | 20 ± 6 | 21 ± 6 | 0.5 |
At the end of the follow-up period, 75 patients had died (16% of overall, Kaplan-Meier 10-year mortality rate 26%), including 31 deaths from HC and 25 deaths from unknown causes ( Table 4 ). Overall, 21 events were classified as SCDs (14 in the medical group and 7 in the myectomy group), including 11 deaths (7 in the medical group and 4 in the myectomy group) and 10 patients who received treatment of a lethal arrhythmia by an AICD (7 in the medical group and 3 in the myectomy group).
| Variable | Total Population (n = 478) | Myectomy (n = 239) | Medical Therapy (n = 239) |
|---|---|---|---|
| Death, any cause | 75 | 20 | 55 |
| Noncardiac death | 19 | 6 | 13 |
| HC-related death | 31 | 9 | 22 |
| Sudden death | 21 | 7 | 14 |
| Operative death | 1 | 1 | 0 |
| Pulmonary hypertension | 1 | 1 | 0 |
| Heart failure | 7 | 0 | 7 |
| Stroke | 1 | 0 | 1 |
| Unknown cause | 25 | 5 | 20 |
| Permanent pacemaker implanted during follow-up | 49 | 28 | 21 |
| Implantable cardioverter-defibrillator implanted during follow-up | 64 | 31 | 33 |
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