Bond giants Pimco and Invesco are facing losses of hundreds of millions on rotten Credit Suisse debt

• Some of the biggest names in fixed income are nursing their wounds after Credit Suisse's rescue.

• Bond giants Pimco and Invesco lost hundreds of millions of dollars, according to data from Bloomberg.

• They held Credit Suisse's AT1 bonds – which were marked down to zero by the Swiss regulator a week ago.

Some of the biggest names in fixed income investing have lost millions of dollars following the rescue of Credit Suisse by its rival UBS last week.

Pimco and Invesco both suffered massive losses because they held the failed Swiss bank's Additional Tier 1 bonds, according to data from Bloomberg.

FINMA, which is Switzerland's top financial regulator, marked the value of all Credit Suisse AT1s down to zero when UBS's takeover of the struggling bank was confirmed.

That wiped out 16 billion francs ($17 billion) worth of value overnight – and left the bond giants nursing their wounds.

AT1s, which are also known as contingent convertible bonds or CoCos, are a riskier type of bank bond that offers a higher yield than assets that are typically considered safer, like government debt.

But the reason for those greater returns is that there's more risk attached to them – because the bank can choose to convert them into shares to prop up its capital and reduce its debt if its financial health falls beneath a certain level.

Pimco had $807 million worth of Credit Suisse CoCos written off when the bank was rescued, according to Bloomberg – while Invesco held around $370 million worth of AT1 debt at the time of the takeover.