HRS: Study shows Riata leads worse off in terms of survival

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BOSTON—Adding to the hoopla surrounding Riata research, a late-breaking study presented May 10 at the 33rd annual scientific sessions of the Heart Rhythm Society showed that survival for Riata (St. Jude Medical), but not Riata ST leads, was significantly lower than that of the Quattro Secure leads (Medtronic). However, the authors noted that this could be due to the fact that Riata ST leads had a shorter follow-up period.

A recent study published in Heart Rhythm March 26 shed light on possible problems related to the Riata leads after researchers found that high-voltage failures in Riata and Riata ST implantable cardioverter-defibrillator (ICD) leads and not externalized conductors may be the culprit behind deaths in some patients who received the devices.

In the current study, Raed Abdelhadi, MD, of the Minneapolis Heart Institute,  and colleagues conducted a seven-center trial to assess the long-term survival of Riata and Riata ST leads compared to the Quattro Secure implantable cardioverter-defibrillator (ICD) leads after the recent Riata lead recall due to insulation defects.

“As you know, Riata and Riata ST are prone to … insulation defects which can result in lead malfunction and externalization of the conductor cables,” Abdelhadi said during a morning press conference. Currently, no multicenter trial data exists that looks at the incidence of Riata or Riata ST ICD lead failure, he added. “Without such data it will be impossible to design advanced paced management strategies for these patients or to advice these patients of the risk.”

Additionally, he added that the factors of such failure, the consequences and the “liability of electrically intact externalized conductors is unclear.”

Abdelhadi outlined the following study goals:

  • Compare survival of the Riata and Riata ST leads to the Medtronic Quattro Secure lead related to all cause failure and electrical malfunction;
  • Determine lead failure rates;
  • Assess size of Riata lead failure and consequences;
  • Evaluate lead performance in the presence of externalized conductors; and
  • Identify Clinical predictors for lead trials.

The seven-center observational trial included adults implanted with Riata or Riata ST leads.

The researchers defined lead failure as:

  • Abnormal impedance resulting in lead replacement;
  • Electrical noise;
  • An elevated threshold R wave resulting in lead placement; and
  • Externalized conductors were considered failures even if they were electrically intact.
Quattro Secure data was obtained from a previous study published last year in Circulation.

Abdelhadi said that 1,081 patients received a Riata or Riata ST lead between 2002 and 2010. Of those, 774 patients received an 8F Riata lead and underwent an average follow-up period of 4.2 years. Additionally, 307 patients received a 7F Riata ST lead with an average follow-up period of 3.3 years.

“The difference in follow-up was statistically significant,” he said.

Patients had an average age of 64 years, an average ejection fraction of 28 percent and three-quarters were male. On follow-up, 27 percent received appropriate ICD shocks.

“As of the fourth quarter of 2011, 66 percent of the leads were active and functioning normally,” Abdelhadi said. At this same follow-up point, 28 percent of leads were removed from service for causes other than failure.

During the study, there were 67 incidences of lead failure resulting in a 6.2 percent incidence of all-cause failure. Additionally, 47 leads were reported to have electrical malfunction (4.3 percent incidence rate). Of the 47 leads that experienced an electrical malfunction, seven had externalized conductors. However, 20 leads with externalized conductors had normal function, Abdelhadi said.

Of the total 1,081, 110 were examined for externalized conductors—10 percent of the cohort.

The researchers reported that Riata leads saw significantly worse survival when compared to the Quattro Secure; however, Riata ST lead survival rates were not significantly different from Quattro Secure leads.

“It is important to note that the follow-up period of the Riata ST lead was shorter than that of the Riata lead.” Very few Riata ST leads had a follow-up that was beyond four years. These results were the same for electrical malfunction.

“The all-cause failure rate for the Riata lead was 1.93 percent per patient year, for the Riata ST lead the failure rate was 0.5 percent per patient year and for Quattro Secure it was 0.43 percent per patient year,” Abdelhadi offered. These rates for electrical malfunction were 1.34 percent and 0.4 percent for the Riata and Riata ST lead, respectively. 

“We were unable to identify any predictors for both the Riata and Riata ST lead failures,” he added. Factors investigated included age, gender, ejection fraction, indication for implantation, cardiac disease and lead position.

The author called the fact that only 10 percent of leads were examined for presence externalized conductors a limitation of the trial.

“Our data suggest that externalized conductors are common in dual Riata leads,” Abdelhadi added. “Nearly a quarter of externalized conductors in this study were malfunctioning.” Additionally, he added that oversensing was a frequent sign of lead failure.

When asked how the current study relates to the much discussed Hauser et al study, Abdelhadi said, “This is a completely different study. That study looked at lead-related death,” he added.  “Here we looked at all-cause failure.”

When asked whether Abdelhadi expects to receive flak for the current study he summed: “These are all scientific papers that in my mind should be addressed or discussed in a peer review process. I am not sure that I want this to be a press issue. This is data from seven centers that we feel very strong and comfortable with. Hopefully it will stay positive by everybody because our goal is to help patients and to see how to manage them.”